diff --git a/docs/ALARM-AND-DEFENSE.md b/docs/ALARM-AND-DEFENSE.md new file mode 100644 index 0000000..dd43422 --- /dev/null +++ b/docs/ALARM-AND-DEFENSE.md @@ -0,0 +1,273 @@ +# alarm pheromones, threat response, and defense + +how ants detect threats, communicate danger, and defend the colony. relevant to +features #2 (repellent pheromone) and #6 (alarm pheromone) in REALISM-IDEAS.md. + + +## what triggers alarm pheromone release + +main triggers — all physical/biological, not environmental chemicals: + +- physical disturbance of the nest or individual ant +- predator detection (olfactory, visual, or tactile) +- crushing or injury of nestmates (damaged ants release alarm compounds + from ruptured glands) +- intrusion by non-nestmates into the colony + +ants exhibit "enemy specification" — dangerous species are more effective at +evoking alarm than less threatening ones. this is not a generic startle reflex. + +### specific predator triggers + +- army ants (Neivamyrmex spp.): minor workers of Pheidole desertorum and + P. hyatti initiate panic alarm leading to nest evacuation specifically when + they detect approaching army ants. distinct from response to other threats. +- the spider Habronestes bradleyi exploits Iridomyrmex purpureus alarm + pheromone (6-methyl-5-hepten-2-one) as a kairomone — the predator is + literally attracted by the alarm signal, turning the defense against the ants. + +### what about plants, chemicals, environmental hazards? + +no strong evidence for specific plants triggering alarm pheromone release. +some alarm compounds (citronellal) exist in plant essential oils, so +cross-reactivity is plausible but undocumented. + +some alarm compounds (citral, 2-heptanone, 4-methyl-3-heptanone) have +antifungal properties. the alarm system may have originally evolved for +pathogen defense, with the danger-signaling function coming later. + +### environmental threat responses + +- flooding: Solenopsis invicta detects rising water and responds with + colony-wide raft formation — workers link legs to create buoyant living + rafts, brood placed on top. instinctive, coordinated. +- chemical contamination: cadmium exposure degrades olfactory sensitivity in + fire ants, reducing bait search efficiency. at higher doses, reverses + attraction to food odorants entirely. ants detect contamination through + impaired function more than active avoidance. +- fire: no specific "fire alarm" behavior. fire substantially changes ant + communities, recovery takes years. treated as a disturbance ecology question, + not real-time detection. + + +## alarm is graduated, not binary + +graduated in at least three ways: + +### concentration-dependent intensity + +in Pogonomyrmex badius (harvester ant): + +low intensity: +- increased locomotion +- antennae/head waving +- looping movements +- periodic gaster-lowering to substrate + +high intensity: +- faster locomotion +- tighter circling +- mandible opening (gaping) +- reduced antennae waving (attention shifts from sensing to combat readiness) + +### multi-component chemical modulation + +in Oecophylla longinoda (weaver ant): +- major components (1-hexanol, hexanal) trigger alert and attraction +- minor, less volatile components act as markers for attack +- creates a staged escalation: volatiles spread first (alert), heavier + compounds arrive later (attack cue) +- hexanal is the most volatile — spreads fastest, causes head-raising and + jaw-opening +- hexanol is less volatile, recruits nestmates to the source + +most alarm compounds fall in the C6-C10 molecular weight range, selected for +high volatility and rapid fade-out. + +### context-dependent response (distance from nest) + +- near the nest: alarm pheromone triggers defensive/aggressive behavior + (attack the threat) +- far from the nest (foraging area): same pheromone triggers flight/dispersal + (flee from the threat) + +same chemical, different interpretation based on spatial location. + + +## alarm cascading and propagation + +### positive feedback mechanics + +alarmed ants produce alarm pheromone, which recruits and alarms additional +ants, who produce more pheromone. structurally similar to trail pheromone +reinforcement. + +in territory-conflict models, peaceful ants encountering alarm pheromone +transition to aggressive state, producing their own alarm pheromone — classic +autocatalytic cascade. + +### spread speed + +determined by component volatility. volatile components (hexanal) expand the +active space rapidly; heavier components diffuse more slowly. + +Wilson & Bossert (1963) established the theoretical framework: the "active +space" (zone where concentration >= detection threshold) expands rapidly then +contracts as the compound evaporates. for typical alarm compounds, the signal +dies out within a few minutes unless reinforced. + +number of alarmed nodes decays linearly with network distance from the source. + +### built-in dampening (alarm does NOT spiral out of control) + +- volatility is the primary brake: alarm compounds are specifically selected + for rapid evaporation (low molecular weight, C6-C10). the signal + self-extinguishes. +- no reinforcement = fade-out: if the threat is removed, no new pheromone is + deposited, and the existing signal evaporates within minutes. +- linear decay with distance: the cascade weakens with each hop through the + network rather than amplifying. + +the system is designed for fast on, fast off — the opposite of trail pheromone +which is selected for persistence. + + +## defensive strategies by species + +### flee + +- Pheidole desertorum, P. hyatti: detect army ant (Neivamyrmex) approach, + evacuate nest with brood. panic alarm. + +### multi-phase defense + +- Pheidole obtusospinosa: super majors block nest entrance with enlarged heads + (phragmosis), then switch to aggressive combat outside. + +### autothysis (self-explosion) + +- Colobopsis explodens and ~15 Colobopsis spp.: minor workers rupture their + bodies, releasing bright yellow, sticky, toxic secretion. used as an INITIAL + resort, not a last resort. + +### chemical spray + +- Formica rufa and other Formicinae: spray formic acid from acidopore (tip of + gaster). bite wound first, then spray acid into the wound. effective against + arthropods and even wood-boring beetles. + +### trap-jaw strike + +- Odontomachus bauri: mandibles close at 35-64 m/s — one of the fastest + movements in the animal kingdom. strike against substrate launches the ant + into the air for escape. strike against intruder for ejection. + +### entrance blockade (phragmosis) + +- Colobopsis majors, P. obtusospinosa super majors: use enlarged heads as + physical plugs at nest entrances. + +### caste-based defensive labor + +- P. obtusospinosa: super majors specialize in entrance-blocking (passive) + and combat (active). minors handle brood evacuation. regular majors do both. +- Colobopsis: minor workers are the suicide bombers (autothysis). major + workers are the entrance blockers. + + +## alarm interaction with other pheromones + +### alarm + trail pheromone + +alarm does NOT simply suppress trail-following. it can redirect it: +- ants may follow trails toward a threat for defense +- or away from a threat for evacuation +- context (distance from nest, threat intensity) determines which program wins + +alarm and trail pheromones operate on different chemical channels (different +compounds, different glands — mandibular for alarm vs Dufour's/poison for +trail in many species). an ant can potentially process both simultaneously. + +### foraging disruption + +alarmed ants leave their nest pile and stop normal foraging. but given alarm +pheromone volatility (fades in minutes), foraging disruption is inherently +short-lived for localized threats. + +recovery time: not well-quantified, but the volatility constraint means the +chemical signal clears within minutes. behavioral recovery follows shortly +after. the system is tuned for rapid return to baseline. + + +## simulation relevance + +for the alarm pheromone channel (feature #6): + +key parameters: +- separate channel from trail pheromone (world.A is available, or a second + world texture per INFRASTRUCTURE.md) +- high diffusion rate, fast decay (minutes, not hours) +- response is context-dependent: fight near nest, flee far from nest +- graduated intensity via concentration thresholds, not just on/off +- positive feedback with built-in decay (volatile = self-extinguishing) +- caste-specific responses if caste system is implemented + +the multi-component timing (fast alert component + slow attack component) could +be modeled as: +- option A: two sub-channels with different diffusion rates +- option B: single channel with behavioral thresholds (low = alert, high = + attack) +- option B is simpler and captures the essential dynamics + +for the repellent pheromone (feature #2, already has infrastructure): +- deposited at trail junctions to depleted food, not along entire failed paths +- ants encountering it U-turn or zigzag +- longer half-life than trail pheromone (~2x) +- junction detection is the hard part — requires knowing when an ant is at + a bifurcation point vs mid-trail + + +## sources + +Alarm Communication + AntWiki antwiki.org/wiki/Alarm_Communication + +Alarm pheromone processing in the ant brain + PMC2912167 + +Alarm pheromone composition in fungus-growing ants + PMC5371636 + +Alarm pheromone and alarm response of clonal raider ant + PMC9941220 + +Insect alarm pheromones in response to predators + Basu 2021 (WSU) + +Alarm Pheromone — ScienceDirect Topics + +Multi-phase defense by Pheidole obtusospinosa + PMC3014660 + +Colobopsis explodens + Wikipedia + +Formica rufa + Wikipedia + +Trap-jaw ant mandible mechanism + J Exp Biol 226(10) jeb245396 + +Ant territory formation model with alarm pheromones + ScienceDirect S0025556425001245 + +Fire ant flood raft behavior + AMDRO + +Cadmium olfactory neurotoxicity in fire ants + ScienceDirect S0269749124016592 + +Wilson & Bossert 1963 + Theoretical framework for pheromone active space dynamics + +The Ants Chapter 7 — AntWiki diff --git a/docs/FOOD-QUALITY.md b/docs/FOOD-QUALITY.md new file mode 100644 index 0000000..884cf2a --- /dev/null +++ b/docs/FOOD-QUALITY.md @@ -0,0 +1,508 @@ +# food quality perception and evaluation in ants + +reference doc for food quality mechanics in the simulation. all claims sourced +from published research. confidence levels noted where information is +extrapolated or less well-established. + + +## 1. sensory detection: what ants can taste + +### sensory organs + +ants detect food using gustatory (taste) sensilla distributed across multiple +body parts. the primary taste organs are: + +- **foreleg tarsi** — contact chemoreceptors. in fire ants (Solenopsis invicta), + the foreleg tarsi play a MORE important role in sucrose detection than the + antennal flagellum. sensilla chaetica, trichoid II, and basiconica I/II all + have a clear pore at their tip for chemoreception. +- **antennal flagellum** — both olfactory and gustatory sensilla. used for + close-range assessment and during trophallaxis. +- **maxillary and labial palps** — mouthpart sensilla for evaluation during + ingestion. +- **pharynx** — internal gustatory sensilla that evaluate food as it enters the + crop. + +**confidence: high** — well-established insect morphology, confirmed across +multiple ant species. + +### gustatory receptor (GR) genes + +the number of GR genes varies by species and correlates with dietary breadth: + +| species | common name | GR genes | +|--------------------------|---------------------|----------| +| Linepithema humile | Argentine ant | 96 | +| Apis mellifera | honeybee | 10 | +| Drosophila melanogaster | fruit fly | 68 | + +ant GR genes fall into four clades: CO2 receptors, GR43a-like (internal +fructose/nutrient sensors), sugar receptors, and bitter receptors. generalist +species tend to have expanded bitter receptor families, presumably broadening +the range of plant secondary metabolites they can detect. + +**confidence: high** — genomic data from sequenced ant genomes. + +### sugars + +**preference hierarchy**: sucrose > glucose >> fructose (in fire ants) + +- fire ant workers strongly prefer sucrose and glucose but show only weak + attraction to fructose. +- SinvGr43a is a fructose-responsive gustatory receptor in S. invicta, but it + acts primarily as an INTERNAL nutrient sensor (linked to neuropeptide + regulation and lipid metabolism) rather than a peripheral taste receptor. +- concentration matters: ants discriminate between sucrose concentrations. + 1.0 M sucrose elicits strong behavioral responses (trail-laying, feeding), + while 0.01 M sucrose does not. in Lasius niger experiments, 0.2 M sucrose + led to lower food acceptance than 1.0 M. +- threshold detection in related insects: ~10 mM for antennal sensilla, + ~100 mM for tarsal sensilla (moth data — ant-specific thresholds likely + similar order of magnitude but not precisely established). + +**confidence: high** for preference hierarchy and concentration discrimination. +moderate for exact threshold values in ants specifically. + +### amino acids and proteins + +- ants discriminate essential amino acids (EAAs) from non-essential ones. +- when deficient in both carbs and EAAs and offered sucrose+EAA vs + sucrose+non-EAA solutions, ants focused foraging on the EAA solution + regardless of amino acid:carbohydrate ratio. +- S. invicta workers showed strong preference for leucine (an EAA) over other + tested amino acids, with preference intensifying at higher concentrations. +- when choosing between high-protein foods, ants preferred free amino acids + over whole proteins. no preference emerged with high-carb foods. + +**confidence: high** — multiple controlled experiments across species. + +### salts and minerals + +- Solenopsis richteri workers prefer zinc, magnesium, and ammonium. +- sodium preference varies and shows a geographical gradient: ants farther from + the ocean consume more sodium. non-predatory species consume more sodium than + predatory species (predators get sodium from prey). +- salts and acids are attractive at low concentrations but aversive at high + concentrations (inverted U response curve). + +**confidence: high** — field and lab studies. + +### toxins and deterrents + +- quinine is aversive to Lasius niger. +- high concentrations of caffeine in sucrose reduced feeding in Oecophylla + smaragdina (weaver ants). +- alkaloids reduced feeding in Ectatomma ruidum. +- leaf-cutter ants (Atta, Acromyrmex) avoid leaves containing anti-fungal + terpenoids that would harm their cultivar fungus. + +**confidence: high** — behavioral assays with known compounds. + + +## 2. nutritional assessment and post-ingestive feedback + +### speed of assessment + +ants can compensate for nutritional deficiencies in their colony in under 10 +minutes. this is fast enough that it likely involves rapid nutrient sensing +rather than slow learning/feedback loops. + +### post-ingestive feedback mechanism + +the term "post-ingestive feedback" refers to the process by which nutrients +interact with receptors on enteroendocrine cells in the gut after ingestion. +these cells secrete hormones that signal the brain and other tissues about +nutrient composition, food texture, and meal size. + +mechanistic details (primarily from Drosophila, likely conserved in ants): +- Dh44 neurons are necessary and sufficient for post-ingestive nutrient sensing +- gut-to-brain signaling uses neuropeptide pathways +- the internal fructose sensor GR43a (mentioned above) is part of this system, + linking circulating nutrient levels to feeding behavior and lipid metabolism + +**confidence: moderate** — the gut-sensor mechanism is well-established in +Drosophila. the specific molecular pathways in ants are inferred by homology +rather than directly demonstrated. the behavioral outcomes (rapid compensation) +are directly measured in ants. + +### learning and memory about food quality + +- ants can learn which foods are nutritious vs empty calories. foraging + motivation and food quality affect both route memory formation speed and the + likelihood of returning to a food source. +- two parameters dominate quality assessment at a food site: + 1. **amount of food available** — initially dominates the decision to return + 2. **reliability of food encounter** — takes precedence after a few visits +- ants may learn the location of higher-quality food faster, with most ants + eventually congregating at the best source. + +**confidence: high** — direct behavioral experiments. + + +## 3. the geometric framework for nutrition + +### core concept + +the geometric framework (developed by Simpson & Raubenheimer) models nutrition +as a multi-dimensional space where each axis represents a nutrient. animals have +an "intake target" — an optimal point in this space — and regulate their feeding +to approach it. + +### how it applies to ant colonies + +- colonies have separate appetites for protein and carbohydrate, enabling them + to compensate for changes in nutrient density and to select among + nutritionally complementary foods. +- **workers need carbohydrates** (energy for foraging, maintenance). +- **larvae need protein** (growth, development). +- this creates a fundamental tension: the colony must collect both, but the + ratio shifts with brood load. + +### colony-level regulation + +- in Monomorium pharaonis (pharaoh's ant), colonies defended a slightly + carbohydrate-biased intake target. +- when confined to imbalanced protein:carbohydrate (P:C) diets, colonies used a + "generalist equal-distance strategy": overharvesting BOTH protein and + carbohydrate to reach the target ratio, rather than prioritizing one. +- ants regulate macronutrient intake at both individual and colony levels, + maintaining their specific elemental body composition. + +### what happens when the balance is off + +- when carbohydrate-supplemented, fire ant colonies consumed less cricket and + specifically avoided high-lipid ovaries. +- when amino-acid-supplemented, they consumed less male cricket (lower lipid, + higher protein). +- this demonstrates independent regulation of at least protein, carbohydrate, + and lipid. + +**confidence: high** — the geometric framework is well-validated across multiple +ant species and other social insects. + + +## 4. food quality and recruitment behavior + +### the pharaoh's ant baseline (Monomorium pharaonis) + +- trail-marking ants deposited significantly more pheromone when returning from + high-quality food (1.0 M sucrose) vs low-quality food (0.01 M sucrose). +- at low food quality, there was no significant difference in marking intensity + between fed and unfed trail-marking ants — the quality signal disappeared. + +### Lasius niger (black garden ant) + +- deposits up to 22x more pheromone within 10 cm of a food source compared to + near the nest. +- uses an all-or-nothing individual response to food quality (binary: mark or + don't mark), which contrasts with Pharaoh's ant graded response. +- L. niger is proficient at visual-based orientation, so it's less reliant on + pheromone trails than pharaoh's ants. +- the presence of existing pheromone trails does NOT influence an individual + ant's subjective reward evaluation — they assess food quality independently. + +### general principles across species + +- the more rewarding a food source, the higher the pheromone concentration on + the trail. +- some species use multiple pheromones: a long-lasting exploration pheromone + (weak recruitment) and a shorter-lasting exploitation pheromone (strong + recruitment). the exploitation pheromone is deposited preferentially for + high-quality food. + +### tandem running (Temnothorax spp.) + +- tandem running is a one-to-one recruitment method where a leader guides a + follower from nest to food. +- tandem running is favored when food sources are hard to find, differ in + energetic value, and are long-lasting. +- colonies can adaptively allocate foragers across sources of different quality + using tandem running. +- followers learn specific routes from leaders — 90% of tandem leaders guided + followers along routes they had originally learned as followers themselves. +- gene expression: learning and memory genes are specifically upregulated in + scouts and tandem-followers. + +### response to environmental change + +- ants strongly upregulate pheromone deposition immediately after experiencing + an environmental change (e.g., food source moves or changes quality). +- VULNERABILITY: pheromone-based positive feedback can trap colonies at local + optima. if a poor feeder is established first, the pheromone trail can + outcompete incipient trails to a better source added later. this is a known + failure mode of stigmergic systems. + +**confidence: high** — extensive experimental literature across species. + + +## 5. food source evaluation and decision-making + +### comparing multiple food sources + +- ants integrate food quality with foraging cost (distance, danger). +- the marginal value theorem (MVT) predicts: leave a food patch when the + current rate of energy gain drops to the average expected rate for the habitat. +- in practice: ants stay longer at patches that are farther apart or when + current patches are poor (both increase travel-cost-to-benefit ratio). + +### distance vs quality tradeoff + +- closer low-quality food vs farther high-quality food: ants can get trapped at + the closer source due to pheromone positive feedback (see vulnerability above). +- learning speed differences help: ants learn routes to higher-quality food + faster, which can partially overcome the distance disadvantage. +- small differences in learning speed for different food qualities can drive + efficient collective foraging at the colony level. + +### memory and reassessment + +- ants DO remember food source locations and quality. +- assessment updates over multiple visits — initial visits weight "amount of + food" heavily, later visits weight "reliability" more. +- private information (individual memory) can sometimes trap colonies at local + optima, independent of pheromone effects. +- ants do NOT appear to actively correct erroneous pheromone trails — trails + decay naturally rather than being "erased." + +**confidence: high** for behavioral patterns. the MVT application to ants is +well-supported theoretically but ants don't perfectly optimize — they use +heuristics that approximate MVT predictions. + + +## 6. trophallaxis and food quality communication + +### what gets transferred + +trophallactic fluid in Camponotus floridanus contains far more than just food: + +- **nutrients** — sugars, amino acids, lipids +- **proteins** — both digestion-related and non-digestion-related. many are + regulators of growth, development, and behavioral maturation. +- **juvenile hormone III (JH)** — a key developmental regulator. when workers' + food was supplemented with JH, larvae they reared via trophallaxis were TWICE + as likely to complete metamorphosis and became larger workers. +- **JH esterase paralogs** — enzymes that break down JH, providing a + regulatory counterbalance. +- **cuticular hydrocarbons (CHCs)** — nestmate recognition cues. +- **small RNAs (microRNAs)** — potential gene expression regulators. + +### quality information transfer + +- food receivers perceive the odor of food delivered by the donor and associate + it with the food reward. +- through individual experience, workers evaluate the characteristic information + of food and assess its quality. +- social information can OVERRIDE individual assessment: carpenter ants + receiving social instructions will consume food they would otherwise reject, + even toxic food, despite noxious effects. social instruction overrides + individual evaluation. + +### the crop as a social stomach + +- the crop (foregut) stores liquids separately from the midgut. +- food intended for sharing is kept available for trophallaxis without being + fully digested. +- this allows ants to act as mobile food storage and distribution units. + +**confidence: high** — proteomic and molecular analysis of trophallactic fluid +is well-established, particularly in Camponotus floridanus. + + +## 7. species-specific food quality concerns + +### fire ants (Solenopsis invicta) + +- omnivorous, regulate protein/carb/lipid independently. +- prefer sucrose and leucine, with preference intensifying at higher + concentrations. +- prefer single-component solutions over multi-component mixtures. +- larvae display independent appetites for solid protein, amino acid solution, + and sucrose solution. +- when infected with SINV-1 virus: reduced foraging, declined lipid intake, + shifted preference toward carbohydrate-rich foods. + +### leaf-cutter ants (Atta, Acromyrmex) + +food quality is evaluated at TWO levels: for the ant AND for the fungal +cultivar. + +- **leaf selection criteria**: plant chemistry, nutrient content, tenderness, + vein thickness, trichome density, endophyte load. +- prefer young leaves with soft cuticles, fewer defenses, higher nutritional + value. +- **fungal feedback**: ants detect chemical signals from the fungus. if a leaf + type is toxic to the fungus, the colony stops collecting it. this is a + learned colony-level response. +- fungus gardens preferentially break down simpler, more digestible substrates + first. +- the fungus produces specific enzyme profiles in response to different plant + substrates (different protein expression for different leaves). +- foraged material (fruits, flowers, leaves) is combined to maximize cultivar + performance — a multidimensional nutritional optimization. +- trace mineral management: concentrations of toxic trace minerals (Cu, Mn, Zn) + in foraged leaves peak near the macronutrient intake target, suggesting + active regulation of micronutrient toxicity. + +### harvester ants (Pogonomyrmex spp.) + +- seed specialists. selection based on multiple factors: + - caloric reward (energy density) + - seed size (prefer 3-30 mg in P. rugosus) + - protein and energy content (P. salinus preferentially selects + Lepidium papilliferum seeds for their higher protein/energy content) + - handling time and travel cost +- individual foraging choices are labile — converge on the most energetically + profitable species over time. +- colony dietary history influences individual seed preferences. + +### honeypot ants (Myrmecocystus spp.) + +- specialized repletes (living storage vessels) store liquid carbohydrates. +- foragers collect sweet exudates from cynipid galls and regurgitate to repletes + via trophallaxis. +- replete honey composition: primarily glucose and fructose, ~67g sugar per + 100g, pH 3.85. +- the crop keeps food separated from the midgut so it remains available for + redistribution without being digested. +- when food is scarce, the process reverses: repletes regurgitate stored sugar + to feed the colony. + +### Temnothorax spp. (acorn/rock ants) + +- use tandem running rather than mass recruitment. +- stored excess food is sufficient for reducing protein foraging — colonies with + food reserves are less responsive to protein opportunities. +- small colonies respond more strongly to larval demand signals than large ones. + +**confidence: high for fire ants and leaf-cutters** (extensively studied). +moderate for harvester ants (good behavioral data, less molecular detail). +moderate for honeypot ants (descriptive natural history is solid, mechanistic +data is thinner). + + +## 8. larval nutritional signaling + +### the demand chain + +nutritional information flows through a hierarchical demand chain: + + larvae → nurses → foragers → environment + +1. **larvae signal hunger** via non-volatile contact pheromones and begging + behaviors (physical solicitation). +2. **nurses respond** by soliciting food from foragers or from stored reserves. +3. **foragers adjust** foraging effort and target macronutrient composition based + on upstream demand. + +### larval pheromone effects (dose-dependent) + +- workers in colonies WITH larvae increase foraging activity compared to + broodless colonies. +- workers suppress ovarian activation in the presence of larvae (progressive + effect — stronger in smaller colonies). +- the response is dose-dependent: more larvae = stronger foraging drive + + stronger ovarian suppression. + +### specificity of demand + +- the chain is nutrient-specific. ants can match foraging to deficiencies in + single amino acids, suggesting the demand signal carries information about + WHAT is needed, not just "feed me." +- workers shift foraging toward protein-rich sources when larval demand is high + (more brood = more protein foraging). +- in Temnothorax longispinosus, stored excess food alone is sufficient to reduce + protein foraging — the colony tracks its reserves. + +### information propagation in large colonies + +- in small colonies, direct larva-worker contact may suffice. +- in larger colonies, larval pheromones may propagate through the trophallaxis + network: transferred from nurse to forager via oral fluid exchange, carrying + the chemical signal deeper into the nest. +- this is less well-characterized mechanistically than the direct-contact + pathway. + +**confidence: high** for the existence and behavioral effects of the demand +chain. moderate for the specific molecular identity of larval hunger pheromones. +the propagation mechanism in large colonies is plausible but not definitively +demonstrated. + + +## simulation implications + +key parameters to model for food quality in the simulation: + +1. **food quality value (0-255, already allocated in world.R bits 6-13)** + - maps to sugar concentration / caloric density + - affects pheromone deposition intensity (graded or binary per species model) + - affects recruitment strength + +2. **colony nutritional state** + - protein vs carbohydrate balance (two-axis model from geometric framework) + - brood load shifts target toward protein + - deficit in either axis biases forager preferences + +3. **individual forager memory** + - food source location + quality rating + - updates over visits (amount → reliability weighting shift) + - learning speed proportional to food quality + +4. **trophallaxis network effects** + - quality information propagates through social feeding + - social information can override individual assessment + - larval demand propagates upstream through nurses to foragers + +5. **pheromone trail modulation** + - trail intensity proportional to food quality (above some threshold) + - dual-pheromone option: exploration (weak, long-lived) vs exploitation + (strong, short-lived) + - trap risk: established trails to poor sources resist switching + +6. **distance-quality tradeoff** + - not a simple linear comparison — pheromone feedback creates path dependence + - closer poor food can dominate farther good food due to positive feedback + - learning speed differences partially compensate + + +## sources + +- [Preference and effect of gustatory sense on sugar-feeding of fire ants](https://peerj.com/articles/11943/) +- [A fructose-sensitive gustatory receptor in fire ants](https://www.sciencedirect.com/science/article/abs/pii/S0965174825001845) +- [Detection of sweet tastants by insect gustatory receptors](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3910600/) +- [Ant foragers compensate for nutritional deficiencies in the colony](https://www.cell.com/current-biology/fulltext/S0960-9822(19)31458-7) +- [Flexible, but not enough: how an omnivorous ant copes with macronutrient imbalances](https://nsojournals.onlinelibrary.wiley.com/doi/abs/10.1002/oik.11557) +- [Nutritional geometry of Monomorium pharaonis](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0218764) +- [Carbohydrate regulation in relation to colony growth](https://journals.biologists.com/jeb/article/211/14/2224/17598/Carbohydrate-regulation-in-relation-to-colony) +- [Ant nutritional ecology: linking nutritional niche plasticity](https://www.sciencedirect.com/science/article/abs/pii/S221457451400090X) +- [Modulation of pheromone trail strength with food quality in pharaoh's ant](https://www.sciencedirect.com/science/article/abs/pii/S0003347207002278) +- [Lasius niger pheromone deposition near food sources](https://link.springer.com/article/10.1007/s00040-024-00995-y) +- [Trail pheromone does not modulate subjective reward evaluation in L. niger](https://pmc.ncbi.nlm.nih.gov/articles/PMC7540218/) +- [The role of multiple pheromones in food recruitment](https://journals.biologists.com/jeb/article/212/15/2337/18424/The-role-of-multiple-pheromones-in-food) +- [Trail pheromones of ants (review)](https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-3032.2008.00658.x) +- [Food information acquired socially overrides individual assessment](https://link.springer.com/article/10.1007/s00265-016-2216-x) +- [Social transmission of information via trophallaxis](https://royalsocietypublishing.org/doi/10.1098/rspb.2017.1367) +- [Oral transfer of chemical cues, growth proteins and hormones in social insects](https://elifesciences.org/articles/20375) +- [Molecular evolution of JH esterase-like proteins in trophallactic fluid](https://www.nature.com/articles/s41598-018-36048-1) +- [Preferences for sugars and amino acids in nectar-feeding ants](https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2656.2004.00789.x) +- [Effects of macro- and micro-nutrients on feeding responses by ants](https://www.nature.com/articles/s41598-024-56133-y) +- [Dietary diversity, sociality, and the evolution of ant gustation](https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2023.1175719/full) +- [Feeding preferences for sugars and amino acids in fire ants](https://www.mdpi.com/2075-4450/17/3/258) +- [Regulation of diet in the fire ant](https://link.springer.com/article/10.1023/A:1020835304713) +- [Route learning during tandem running in Temnothorax](https://journals.biologists.com/jeb/article/223/9/jeb221408/223803/Route-learning-during-tandem-running-in-the-rock) +- [Teaching in tandem-running ants](https://pubmed.ncbi.nlm.nih.gov/16407943/) +- [Tandem-running and scouting characterized by learning/memory gene upregulation](https://pubmed.ncbi.nlm.nih.gov/30903719/) +- [Temnothorax adjusts tandem running when distance exposes them to greater risks](https://link.springer.com/article/10.1007/s00265-018-2453-2) +- [Ant larvae regulate worker foraging behavior and ovarian activity dose-dependently](https://pmc.ncbi.nlm.nih.gov/articles/PMC5015688/) +- [Stored excess food reduces protein foraging in Temnothorax](https://link.springer.com/article/10.1007/s00265-025-03683-4) +- [Foraging and feeding independently regulated in clonal raider ant](https://link.springer.com/article/10.1007/s00265-021-02985-7) +- [Ants adjust pheromone deposition to changing environment](https://pmc.ncbi.nlm.nih.gov/articles/PMC4590477/) +- [Private information can trap colonies in local feeding optima](https://journals.biologists.com/jeb/article/219/5/744/16615/Private-information-alone-can-trigger-trapping-of) +- [Small differences in learning speed drive efficient collective foraging](https://link.springer.com/article/10.1007/s00265-018-2583-6) +- [Re-visiting plentiful food sources in desert ants](https://pmc.ncbi.nlm.nih.gov/articles/PMC3389614/) +- [Fungal cultivar of leaf-cutters produces specific enzymes per plant substrate](https://pmc.ncbi.nlm.nih.gov/articles/PMC5118115/) +- [Multidimensional nutritional niche of leaf-cutter fungus provisioning](https://pmc.ncbi.nlm.nih.gov/articles/PMC9292433/) +- [Evolutionary innovation of nutritional symbioses in leaf-cutters](https://pmc.ncbi.nlm.nih.gov/articles/PMC4553616/) +- [Seed selection by Pogonomyrmex rugosus](https://pubmed.ncbi.nlm.nih.gov/27257121/) +- [Flexible seed selection by Pogonomyrmex occidentalis](https://link.springer.com/article/10.1007/BF00164118) +- [Honeypot ant (Myrmecocystus) — Wikipedia](https://en.wikipedia.org/wiki/Honeypot_ant) +- [Evolutionary origins of repletism in ants](https://blog.myrmecologicalnews.org/2023/05/31/shedding-light-on-the-evolutionary-origins-of-repletism-in-ants/) diff --git a/docs/PHEROMONES.md b/docs/PHEROMONES.md new file mode 100644 index 0000000..3e11d20 --- /dev/null +++ b/docs/PHEROMONES.md @@ -0,0 +1,407 @@ +# Ant Pheromone Biology + +Reference doc on ant pheromone types, chemistry, triggers, and environmental +factors. Organized for simulation design — what matters for modeling, what +the real biology says, and where the data is thin. + + +## Pheromone types + +### Trail pheromones + +Guide nestmates to food, new nest sites, or other resources. Encode distance +and quality information through concentration gradients. + +Gland sources vary by subfamily: +- Poison gland (most Myrmicinae — stinging ants) +- Dufour's gland (most Formicinae — non-venomous ants) +- Pygidial gland, sternal glands, hindgut (various) + +Known compounds by species: + + species compound gland + Atta texana, A. cephalotes methyl 4-methylpyrrole-2-carboxylate poison + Atta sexdens rubropilosa 3-ethyl-2,5-dimethylpyrazine poison + Tetramorium caespitum 70:30 2,5-dimethylpyrazine + EDMP poison + Tetramorium meridionale indole (major) + 4 pyrazines poison + Monomorium pharaonis (E,E)-faranal poison + Myrmica spp. EDMP + homofarnesenes poison + Dufour's + Solenopsis invicta various poison + +Volatility is a feature — trails evaporate in minutes to hours, so paths to +depleted food naturally fade. The evaporation rate is effectively the colony's +spatial memory duration. + +### Alarm pheromones + +Fast-acting signals that trigger either panic (flee) or aggression (attack) +depending on species, colony size, and context. + +Triggers: +- Physical disturbance of nest or individual +- Predator detection (olfactory, visual, or tactile) +- Crushing/injury of nestmates (damaged ants release alarm compounds) +- Intrusion by non-nestmates + +Known compounds: + + compound species gland + 4-methyl-3-heptanone Atta, Pogonomyrmex, Ooceraea mandibular + formic acid Formica, Camponotus poison + n-undecane Camponotus, many Formicinae Dufour's + 2-heptanone Iridomyrmex pruinosus mandibular + 3-octanol Acromyrmex echinatior mandibular + 3-octanone Acromyrmex octospinosus mandibular + (S)-(-)-citronellal Platythyrea punctata mandibular + (S)-(-)-actinidine Platythyrea punctata mandibular + +Behavioral response sequence: stop movement -> swing antennae -> alerted +posture -> species-specific response (flee or attack). Larger species and +larger colonies tend toward aggression; smaller species tend toward evacuation. + +#### Carpenter ant alarm system (formic acid + n-undecane) + +Two-component blend from two different glands: +- Formic acid (poison gland) -> avoidance behavior, move away from source +- n-Undecane (Dufour's gland) -> attraction toward source, approach to attack + +Each component alone produces a distinct response. Together they create the +full alarm sequence: alert, then approach and aggress. Formic acid also +modulates nestmate recognition — puts ants into a heightened discriminatory +state where they're more likely to attack non-nestmates. + +Processed in ~5 specific "alarm-sensitive" glomeruli clustered in the +dorsalmost part of the antennal lobe, relayed to the lateral horn. + +#### What triggers alarm? Plants? Predators? + +No strong evidence for specific plants that trigger false alarm responses, +though some alarm compounds (citronellal) are also found in plant oils, so +cross-reactivity is plausible. Some alarm compounds (citral, 2-heptanone, +4-methyl-3-heptanone) have antifungal properties, suggesting a dual role in +pathogen defense — the alarm system may have originally evolved as an +antimicrobial response. + +Main natural triggers are physical: nest disturbance, predator contact, and +injured nestmates releasing their contents. The "danger zone" concept maps +best to areas where nestmates have been injured or where persistent threats +exist, not to specific environmental chemicals. + +### Repellent / negative pheromone + +Deposited at trail junctions leading to unrewarding branches. Prevents the +colony from getting stuck on depleted food. Key details from Pharaoh's ant +studies: +- Lasts ~2x longer than attractive trail pheromone (~78 min vs ~33 min) +- Ants encountering it U-turn or zigzag +- Deposited specifically at bifurcation points, not along entire failed paths + +Source: Nature 438, 442 (2005) + +### Queen pheromones + +Complex, multifunctional. Known effects: +- Attract workers for queen attendance +- Promote brood care +- Induce nestmate discrimination +- Inhibit larval sexual development (through worker behaviors) +- Suppress reproduction in other queens and workers +- Induce worker policing of reproductive workers +- Mediate queen acceptance/rejection in polygyne colonies + +Chemistry is poorly characterized compared to trail/alarm pheromones. Involves +cuticular hydrocarbons and at least one dedicated odorant receptor (HsOr263 in +Harpegnathos saltator). Difficult to isolate because the signal may be a +complex blend rather than a single compound. + +### Necrophoresis / death pheromones + +Trigger corpse removal for nest hygiene. Dual-signal system: + +1. Loss of "life signals": living ants produce dolichodial and iridomyrmecin + on their cuticle. These disappear within ~60 minutes of death. Their absence + is the initial trigger. + +2. Gain of "death signals": oleic acid and linoleic acid accumulate as the + corpse decomposes. These are the classical necrophoresis triggers. + +Timing: only 15% of freshly killed corpses get removed. Rises to 80% for +corpses 1-6 days post-mortem as fatty acids accumulate. The colony doesn't +panic-clean — it waits for chemical confirmation. + +### Propaganda pheromones + +Used by slave-making (dulotic) ants during raids. Polyergus queens enter +Formica host nests, kill the resident queen, acquire her chemical profile, +and release substances from an enlarged Dufour's gland that reduce worker +aggression. Raiding workers release: +- Manipulative alarm signals (cause panic, disorganized defense) +- Chemical weapons (directly repellent) +- Appeasement substances (reduce aggression toward the raider) + +Stolen brood are chemically imprinted after eclosion, causing them to identify +the slave-maker colony as home. + +### Cuticular hydrocarbons (CHCs) — colony recognition + +Not classical volatile pheromones but contact chemicals on the cuticle. Each +colony has a distinctive CHC profile — a blend of dozens of hydrocarbons that +workers learn and use to distinguish nestmates from non-nestmates. Non-nestmates +are attacked. The postpharyngeal gland stores and distributes CHCs, homogenizing +the colony odor through trophallaxis (food sharing). + +### Recruitment pheromones + +Functionally distinct from trail pheromones in some species. In Leptogenys +diminuta, two gland sources serve different roles: +- Poison gland secretions: orientation cues (where to go) +- Pygidial gland secretions: recruitment stimulus (leave the nest and follow) + +This separation means "follow this path" and "come help" are independent +signals that can be modulated separately. + +### Brood pheromones + +Signals from eggs, larvae, and pupae that attract worker care. Help workers +assess developmental stage and nutritional needs. Part of the demand chain +that links larval nutritional needs -> nurse behavior -> forager food +preferences. Less well-characterized than adult pheromones. + +### Sex / mating pheromones + +Released by virgin queens (gynes) to attract males during nuptial flights. +Less studied than other types. Identified in Polyergus breviceps. + + +## Food quality + +### What "quality" means to ants + +Primarily macronutrient content — the protein-to-carbohydrate (P:C) ratio. +Different colony members need different things: +- Workers need carbohydrates (energy for foraging, maintenance) +- Larvae and queens need protein (growth, egg production) +- Foragers collect for the colony's current needs, relayed through a demand + chain: larvae -> nurses -> foragers + +Sugar concentration is the primary quality axis for foraging workers. In the +key Pharaoh's ant study, 1.0 M sucrose = "high quality" and 0.01 M sucrose = +"low quality." + +Species-specific sugar preferences exist — carpenter ants (Camponotus modoc) +and European fire ants (Myrmica rubra) show selective preferences for specific +mono-, di-, and trisaccharides. Not all sugars are equal. + +### How ants assess quality + +Two mechanisms: +1. Contact chemoreception — tasting with mouthparts and antennae +2. Post-ingestive feedback — evaluating nutritional content after consumption + +Colony-level nutritional regulation follows a "geometric framework" model: +colonies actively balance P:C intake, shifting forager preferences based on +current deficits. A protein-starved colony will recruit more aggressively +to protein sources. + +### How quality modulates pheromone deposition + +The Pharaoh's ant study (Jackson, Holcombe & Ratnieks 2004/2007): +- Trail marking occurs at ~40% frequency among both fed and unfed foragers +- High quality food (1.0 M sucrose) -> significantly more high-intensity + continuous marking +- Low quality food (0.01 M sucrose) -> no significant difference in marking + intensity between fed and unfed ants +- This is a graded individual response — ants modulate marking intensity, + not all-or-nothing + +Contrast with Lasius niger, where trail strength modulation IS all-or-nothing +at the individual level — an ant either marks or doesn't, based on quality. +The difference: Pharaoh's ants live in dark enclosed spaces and rely heavily +on pheromone trails, so they must always produce some trail. L. niger can use +visual orientation and afford to skip trail-laying entirely for poor food. + +Ants also adjust deposition based on environmental uncertainty — they modulate +trail marking in response to changing conditions and their error probability +(Czaczkes et al. 2015). + +### Simulation relevance + +For the sim, food quality maps to a 0-255 value stored in cell metadata bits. +When an ant picks up food, it reads the quality and stores it as cargoQuality. +The deposition multiplier would scale pheromone output — high quality food +gets stronger trails, attracting more ants. The colony naturally converges on +the best source first, then shifts when it depletes. + +"Different types of food" is less important than "different concentrations." +Real ants care about sugar molarity and protein content, not food identity. +For the sim, a single quality scalar captures the essential dynamics. + + +## Pheromone detection + +### Olfactory receptor genes + +Ants have 300-500 odorant receptor (Or) genes — 4-5x more than most insects +(Drosophila has ~60). This expansion predates complex sociality but facilitated +it. A specialized 9-exon Or gene subfamily detects cuticular hydrocarbons and +candidate pheromones. + +### Antennal lobe glomeruli + +Each Or gene roughly corresponds to one glomerulus in the antennal lobe. + + species glomeruli count + Apterostigma cf. mayri ~630 + Camponotus (carpenter) ~430-460 + Apis mellifera (honeybee) ~163 + Drosophila melanogaster ~43 + +Workers have more glomeruli than males, reflecting greater need for chemical +discrimination. Worker and queen antennal lobes differ in composition and +Or expression. + + +## Environmental effects on pheromones + +### Temperature + +High temperatures accelerate degradation. Above ~40C, workers cannot +discriminate previously-marked substrate. Above ~30C, foraging activity drops +partly because trails decay too quickly to be useful. + +Different compounds have different thermal stability: in Tapinoma nigerrimum, +most gaster secretions vanished at 25C, but iridodials persisted up to 55C. +Aphaenogaster senilis secretions resisted elevated temperatures better. + +Pheromone persistence = f(temperature, time since deposition). Both interact — +higher temperature accelerates decay at all time points. + +### Humidity + +Higher humidity slows evaporation of polar pheromone components. Specific +experimental data is sparser than for temperature. The effect is real but +less dramatic than temperature in most contexts. + +### Substrate surface + +Porous surfaces absorb pheromone and release it slowly (longer persistence). +Smooth impermeable surfaces allow faster evaporation (shorter persistence). + +Direct experimental data on ants is thin — the Pharaoh's ant study +(~9 min on plastic, ~3 min on paper) is one of the few quantitative +comparisons. The physics is well understood but species-specific measurements +are rare. + +### Volatility as design feature + +Trail pheromone volatility provides automatic negative feedback — trails to +depleted food fade without any active erasure. The evaporation rate sets the +colony's spatial memory duration. Too fast = no useful trails. Too slow = +colony gets stuck on depleted paths. Evolution tuned this balance per species +and habitat. + + +## Colony-level dynamics + +### Colony size effects + +Larger colonies have higher collective response thresholds. The relationship +is driven by social feedback — short-range excitatory and long-range +inhibitory interactions. In army ants, increasing colony size causes a +qualitative behavioral shift: organized search patterns in small colonies +give way to spontaneous mass raids in large ones. + +Per-capita interaction rate is roughly scale-invariant — connectivity scales +hypometrically with colony size. + +### Colony state modulates pheromone dynamics + +- Protein-starved colonies shift forager preferences toward protein, changing + trail deposition patterns (more intense marking to protein sources) +- Carbohydrate-rich diets increase social immunity +- Weakly volatile "aggregation" pheromones mark the nest site as a constant + baseline signal anchoring the colony spatially + +### "Colony mood" + +Not a scientific term, but maps onto real dynamics: +- Alarm state propagates as more individuals detect alarm compounds and + release their own (positive feedback cascade) +- Foraging motivation modulated by colony nutritional state — hungry colonies + produce stronger recruitment signals +- The exploration/exploitation balance shifts with colony experience and + environmental conditions + + +## Sources + +Pharaoh's ant pheromone modulation + Jackson, Holcombe & Ratnieks 2004/2007 + ScienceDirect S0003347207002278 + +Negative pheromone + Nature 438, 442 (2005) + +Alarm pheromone processing (carpenter ants) + PMC2912167 + +Alarm pheromone in clonal raider ant + PMC9941220 + +Formic acid + nestmate recognition + J Exp Biol 224(20) jeb242784 + +Necrophoresis dual signals + PNAS 0901270106 + +Corpse chemical changes + J Chem Ecol 10.1007/s10886-013-0365-1 + +Slave-maker chemical warfare + PLOS ONE 10.1371/journal.pone.0147498 + +Queen pheromone properties + Behav Ecol Sociobiol 10.1007/s00265-023-03378-8 + +Trail pheromone review + Morgan 2009, Physiological Entomology + 10.1111/j.1365-3032.2008.00658.x + +Trail pheromone compound list + Natural Product Communications 10.1177/1934578X1400900813 + +Odorant receptors in social insects + Nature Communications 10.1038/s41467-017-00099-1 + +Pheromone-sensitive glomeruli + Proc R Soc B 10.1098/rspb.2006.3565 + +Olfactory system review + PMC8002415 + +Ant olfactory receptor expansion + Vanderbilt (2012) + +Temperature effects on trail following + J Chem Ecol 10.1007/s10886-012-0130-x + +Colony interaction scaling + Frontiers in Ecology and Evolution 10.3389/fevo.2022.993627 + +Collective sensory threshold + PNAS 10.1073/pnas.2123076119 + +Ant nutritional ecology + ScienceDirect S221457451400090X + +Nutrient regulation + Myrmecological News (Csata & Dussutour 2019) + +Exocrine glands of ants + Chemoecology 10.1007/BF01256548 + +Sugar preferences + PMC8371376 + +Pheromone deposition under uncertainty + Czaczkes et al. 2015, PMC4590477 diff --git a/docs/TERRAIN-AND-DECAY.md b/docs/TERRAIN-AND-DECAY.md new file mode 100644 index 0000000..f10da99 --- /dev/null +++ b/docs/TERRAIN-AND-DECAY.md @@ -0,0 +1,227 @@ +# terrain, substrates, and pheromone decay + +how environmental factors affect pheromone persistence. relevant to feature #7 +(substrate-dependent decay) and the worldBlur shader's per-cell decay rate. + + +## substrate effects on persistence + +the key study is Jeanson et al. (2003) on Monomorium pharaonis: + + substrate chemical half-life behavioral preference half-life + plastic ~9 min ~25 min + paper ~3 min ~8 min + +a 3x difference in chemical half-life between two smooth artificial surfaces. +mechanism: paper is porous and wicks the compound away from the surface, +reducing the airborne concentration ants detect. plastic is non-porous, so the +compound sits on top and remains available. + +no comparable controlled study exists for natural substrates (soil, rock, sand, +leaf litter, wood). inferred from physical chemistry: + +- porous substrates (soil, sand, wood, leaf litter) behave more like paper — + absorb compounds, accelerate apparent decay +- non-porous substrates (rock, packed clay) behave more like plastic — keep + compounds on the surface, slower decay +- soil moisture complicates things further (see humidity section) + + +## species variation in baseline trail longevity + +trail pheromone persistence varies enormously across species: + + species trail longevity notes + Solenopsis invicta ~100 sec / <2 min extremely volatile compounds + Monomorium pharaonis ~9 min (plastic) multiple pheromone types + Aphaenogaster albisetosus minutes short-lived + Pachycondyla sennaarensis ~30 min to half gone in 1 hr + Monomorium spp. (general) ~1 day optimal varies + Camponotus (carpenter ants) days hindgut-produced + Daceton armigerum 7+ days poison gland secretion + Eciton spp. (army ants) weeks long-chain, low-volatility + +the range is >100x. species in stable environments with permanent food sources +use long-lasting compounds. species exploiting ephemeral food use volatile ones. + +Pharaoh's ants also use multiple pheromone types with different decay profiles: +a long-lasting attractive pheromone, a short-lived attractive pheromone, and a +short-lived repellent pheromone (~78 min vs ~33 min half-life). + + +## temperature + +the definitive paper is van Oudenhove et al. (2011/2012), studying +Tapinoma nigerrimum and Aphaenogaster senilis. + +key findings: +- above ~40C: workers cannot discriminate marked substrate — pheromone is + effectively destroyed +- above ~30C: foraging activity drops independently, partly because trails + decay too quickly to be useful +- between 25-40C: decay accelerates but trails remain functional +- the 40C threshold is a behavioral cliff, not a smooth curve + +species differ in thermal resilience: +- T. nigerrimum (mass-recruiting): secretions highly volatile. most compounds + vanished even at 25C. only iridodials persisted up to 55C. +- A. senilis (group-recruiting): secretions less volatile, resisted elevated + temperatures better. at 55C, only nonadecene and nonadecane (long-chain + hydrocarbons) persisted. + +pheromone persistence = f(temperature, time since deposition). both interact — +higher temperature accelerates decay at all time points. + +diurnal implications: hot midday temperatures degrade trails laid in morning. +desert species tend to use less volatile compounds (evolutionary compensation +via chemistry rather than behavioral compensation via deposition rate). + + +## humidity and moisture + +less quantitative data than temperature. + +- higher humidity slows evaporation of polar pheromone components +- a cuticle covered with water may hinder both reception and emission of + pheromones — wet conditions impair laying AND sensing, not just persistence +- army ants (Eciton burchellii) increased speed by 30% in response to increased + humidity and rain sounds near the trail, but watering the trail directly did + not cause load-dropping +- extreme humidity (either direction) suppresses foraging entirely + +wet porous substrates (damp soil, wet leaf litter) would absorb pheromone +faster than dry porous substrates, but no controlled study confirms this +quantitatively. + +no direct evidence of ants selecting substrates specifically for pheromone +persistence, though trail-clearing behavior (see below) effectively creates +favorable substrate. + + +## physical trail infrastructure + +### leaf-cutter ant highways (Atta spp.) + +the standout example of ants modifying their environment for trail quality: + +- colonies clear an average of 2,730 meters of trail per year +- individual trails can exceed 200 meters +- networks extend for kilometers cumulatively +- construction/maintenance costs: ~11,000 ant-hours per year + +what they do: remove leaf litter, cut passes through overhanging vegetation, +shift soil to level surfaces. selective clearing — flat objects are ignored, +upright/folded obstructions are removed. + +coordination: trail clearing happens WITHOUT information exchange between +workers. independent effort that adds up to emergent infrastructure. clearing +is triggered by freshly laid pheromone on an obstructed path. + +### minim workers as trail maintainers + +the smallest workers (minims) are always present on trails but never carry +leaves. they deposit pheromone at 83.3% frequency vs 20% for non-minims. +they're dedicated trail maintainers — keeping the chemical signal strong while +larger workers (2.2-2.9mm head width) handle physical clearing. + +### physical + chemical reinforcement loop + +physical clearing creates smooth packed soil (relatively non-porous) which +retains pheromone better than leaf litter. minim workers then maintain high +pheromone concentration. cleared trails retain pheromone better -> strong +pheromone attracts more traffic -> more traffic means more clearing and +reinforcement. positive feedback on two axes simultaneously. + +energetics: not always profitable. depends on workforce composition and patrol +vs carry ratio. can amortize within days or take weeks/months. + + +## emergent highway formation + +the trail network that emerges from substrate-dependent persistence: + +1. substrate quality: non-porous > porous +2. temperature: shade > sun +3. physical modification: cleared > uncleared +4. traffic: popular > unpopular (reinforcement) +5. food quality: rich source > depleted source + +a trail across cool, shaded, packed earth near a rich food source dominates +over a trail across hot, sun-exposed leaf litter near a marginal source. no +ant "decides" this — the pheromone math works out. + +trail bifurcation: at branch points, trail asymmetry (angle, width) influences +decisions alongside pheromone presence. neither geometry nor pheromone alone +dominates — non-hierarchical interaction. + +rapid decay as feature: in fire ants, trail pheromone drops below detection in +~2 minutes. this forces continuous reinforcement, meaning only actively +profitable routes persist. fast decay = responsive colony. + + +## simulation relevance + +for the world texture's terrain type bits (3-5 in world.R): + + terrain type decay multiplier real-world analog + 0 (default) 1.0x generic surface + 1 0.5x (slower) packed earth / rock + 2 1.5x (faster) leaf litter / porous + 3 2.0x (faster) sand / loose soil + 4-7 reserved future use + +the blur shader would read terrain type per cell and multiply the base decay +rate. ants wouldn't "know" about terrain — they'd just find that their trails +last longer on some surfaces, and positive feedback would do the rest. + +temperature could be a global uniform rather than per-cell (simpler), or +per-cell if the simulation adds sun/shade regions. + + +## sources + +Jeanson et al. 2003 + Pheromone trail decay rates on different substrates in Pharaoh's ant + Physiological Entomology 10.1046/j.1365-3032.2003.00332.x + +van Oudenhove et al. 2011 + Temperature limits trail following through pheromone decay + Naturwissenschaften 10.1007/s00114-011-0852-6 + +van Oudenhove et al. 2012 + Substrate temperature constrains recruitment and trail following + J Chem Ecol 10.1007/s10886-012-0130-x + +Bruce et al. 2019 + Infrastructure construction without information exchange in Atta + Proc R Soc B 10.1098/rspb.2018.2539 + +Bruce et al. 2017 + Energetics of trail clearing in Atta + Behav Ecol Sociobiol 10.1007/s00265-016-2237-5 + +Robinson et al. 2008 + Decay rates of attractive and repellent pheromones in foraging trail network + Insectes Sociaux 10.1007/s00040-008-0994-5 + +Morgan 2009 + Trail pheromones of ants (review) + Physiological Entomology 10.1111/j.1365-3032.2008.00658.x + +Effect of trail pheromones and weather on Eciton burchellii + ResearchGate 225346583 + +Minor workers maintain leafcutter ant pheromone trails + ResearchGate 248591651 + +Trail pheromone of Pachycondyla sennaarensis + PMC3281317 + +Monomorium trail pheromone longevity + ScienceDirect S1226861509001034 + +Uncovering the complexity of ant foraging trails + PMC3291321 + +Effect of trail bifurcation asymmetry and pheromone on trail choice + PMC4204274