273 lines
9.5 KiB
Markdown
273 lines
9.5 KiB
Markdown
# alarm pheromones, threat response, and defense
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how ants detect threats, communicate danger, and defend the colony. relevant to
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features #2 (repellent pheromone) and #6 (alarm pheromone) in REALISM-IDEAS.md.
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## what triggers alarm pheromone release
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main triggers — all physical/biological, not environmental chemicals:
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- physical disturbance of the nest or individual ant
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- predator detection (olfactory, visual, or tactile)
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- crushing or injury of nestmates (damaged ants release alarm compounds
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from ruptured glands)
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- intrusion by non-nestmates into the colony
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ants exhibit "enemy specification" — dangerous species are more effective at
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evoking alarm than less threatening ones. this is not a generic startle reflex.
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### specific predator triggers
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- army ants (Neivamyrmex spp.): minor workers of Pheidole desertorum and
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P. hyatti initiate panic alarm leading to nest evacuation specifically when
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they detect approaching army ants. distinct from response to other threats.
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- the spider Habronestes bradleyi exploits Iridomyrmex purpureus alarm
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pheromone (6-methyl-5-hepten-2-one) as a kairomone — the predator is
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literally attracted by the alarm signal, turning the defense against the ants.
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### what about plants, chemicals, environmental hazards?
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no strong evidence for specific plants triggering alarm pheromone release.
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some alarm compounds (citronellal) exist in plant essential oils, so
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cross-reactivity is plausible but undocumented.
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some alarm compounds (citral, 2-heptanone, 4-methyl-3-heptanone) have
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antifungal properties. the alarm system may have originally evolved for
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pathogen defense, with the danger-signaling function coming later.
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### environmental threat responses
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- flooding: Solenopsis invicta detects rising water and responds with
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colony-wide raft formation — workers link legs to create buoyant living
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rafts, brood placed on top. instinctive, coordinated.
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- chemical contamination: cadmium exposure degrades olfactory sensitivity in
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fire ants, reducing bait search efficiency. at higher doses, reverses
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attraction to food odorants entirely. ants detect contamination through
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impaired function more than active avoidance.
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- fire: no specific "fire alarm" behavior. fire substantially changes ant
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communities, recovery takes years. treated as a disturbance ecology question,
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not real-time detection.
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## alarm is graduated, not binary
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graduated in at least three ways:
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### concentration-dependent intensity
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in Pogonomyrmex badius (harvester ant):
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low intensity:
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- increased locomotion
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- antennae/head waving
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- looping movements
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- periodic gaster-lowering to substrate
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high intensity:
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- faster locomotion
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- tighter circling
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- mandible opening (gaping)
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- reduced antennae waving (attention shifts from sensing to combat readiness)
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### multi-component chemical modulation
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in Oecophylla longinoda (weaver ant):
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- major components (1-hexanol, hexanal) trigger alert and attraction
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- minor, less volatile components act as markers for attack
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- creates a staged escalation: volatiles spread first (alert), heavier
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compounds arrive later (attack cue)
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- hexanal is the most volatile — spreads fastest, causes head-raising and
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jaw-opening
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- hexanol is less volatile, recruits nestmates to the source
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most alarm compounds fall in the C6-C10 molecular weight range, selected for
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high volatility and rapid fade-out.
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### context-dependent response (distance from nest)
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- near the nest: alarm pheromone triggers defensive/aggressive behavior
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(attack the threat)
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- far from the nest (foraging area): same pheromone triggers flight/dispersal
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(flee from the threat)
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same chemical, different interpretation based on spatial location.
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## alarm cascading and propagation
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### positive feedback mechanics
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alarmed ants produce alarm pheromone, which recruits and alarms additional
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ants, who produce more pheromone. structurally similar to trail pheromone
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reinforcement.
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in territory-conflict models, peaceful ants encountering alarm pheromone
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transition to aggressive state, producing their own alarm pheromone — classic
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autocatalytic cascade.
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### spread speed
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determined by component volatility. volatile components (hexanal) expand the
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active space rapidly; heavier components diffuse more slowly.
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Wilson & Bossert (1963) established the theoretical framework: the "active
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space" (zone where concentration >= detection threshold) expands rapidly then
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contracts as the compound evaporates. for typical alarm compounds, the signal
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dies out within a few minutes unless reinforced.
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number of alarmed nodes decays linearly with network distance from the source.
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### built-in dampening (alarm does NOT spiral out of control)
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- volatility is the primary brake: alarm compounds are specifically selected
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for rapid evaporation (low molecular weight, C6-C10). the signal
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self-extinguishes.
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- no reinforcement = fade-out: if the threat is removed, no new pheromone is
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deposited, and the existing signal evaporates within minutes.
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- linear decay with distance: the cascade weakens with each hop through the
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network rather than amplifying.
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the system is designed for fast on, fast off — the opposite of trail pheromone
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which is selected for persistence.
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## defensive strategies by species
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### flee
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- Pheidole desertorum, P. hyatti: detect army ant (Neivamyrmex) approach,
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evacuate nest with brood. panic alarm.
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### multi-phase defense
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- Pheidole obtusospinosa: super majors block nest entrance with enlarged heads
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(phragmosis), then switch to aggressive combat outside.
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### autothysis (self-explosion)
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- Colobopsis explodens and ~15 Colobopsis spp.: minor workers rupture their
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bodies, releasing bright yellow, sticky, toxic secretion. used as an INITIAL
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resort, not a last resort.
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### chemical spray
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- Formica rufa and other Formicinae: spray formic acid from acidopore (tip of
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gaster). bite wound first, then spray acid into the wound. effective against
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arthropods and even wood-boring beetles.
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### trap-jaw strike
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- Odontomachus bauri: mandibles close at 35-64 m/s — one of the fastest
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movements in the animal kingdom. strike against substrate launches the ant
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into the air for escape. strike against intruder for ejection.
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### entrance blockade (phragmosis)
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- Colobopsis majors, P. obtusospinosa super majors: use enlarged heads as
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physical plugs at nest entrances.
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### caste-based defensive labor
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- P. obtusospinosa: super majors specialize in entrance-blocking (passive)
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and combat (active). minors handle brood evacuation. regular majors do both.
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- Colobopsis: minor workers are the suicide bombers (autothysis). major
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workers are the entrance blockers.
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## alarm interaction with other pheromones
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### alarm + trail pheromone
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alarm does NOT simply suppress trail-following. it can redirect it:
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- ants may follow trails toward a threat for defense
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- or away from a threat for evacuation
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- context (distance from nest, threat intensity) determines which program wins
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alarm and trail pheromones operate on different chemical channels (different
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compounds, different glands — mandibular for alarm vs Dufour's/poison for
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trail in many species). an ant can potentially process both simultaneously.
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### foraging disruption
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alarmed ants leave their nest pile and stop normal foraging. but given alarm
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pheromone volatility (fades in minutes), foraging disruption is inherently
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short-lived for localized threats.
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recovery time: not well-quantified, but the volatility constraint means the
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chemical signal clears within minutes. behavioral recovery follows shortly
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after. the system is tuned for rapid return to baseline.
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## simulation relevance
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for the alarm pheromone channel (feature #6):
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key parameters:
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- separate channel from trail pheromone (world.A is available, or a second
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world texture per INFRASTRUCTURE.md)
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- high diffusion rate, fast decay (minutes, not hours)
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- response is context-dependent: fight near nest, flee far from nest
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- graduated intensity via concentration thresholds, not just on/off
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- positive feedback with built-in decay (volatile = self-extinguishing)
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- caste-specific responses if caste system is implemented
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the multi-component timing (fast alert component + slow attack component) could
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be modeled as:
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- option A: two sub-channels with different diffusion rates
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- option B: single channel with behavioral thresholds (low = alert, high =
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attack)
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- option B is simpler and captures the essential dynamics
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for the repellent pheromone (feature #2, already has infrastructure):
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- deposited at trail junctions to depleted food, not along entire failed paths
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- ants encountering it U-turn or zigzag
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- longer half-life than trail pheromone (~2x)
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- junction detection is the hard part — requires knowing when an ant is at
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a bifurcation point vs mid-trail
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## sources
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Alarm Communication
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AntWiki antwiki.org/wiki/Alarm_Communication
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Alarm pheromone processing in the ant brain
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PMC2912167
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Alarm pheromone composition in fungus-growing ants
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PMC5371636
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Alarm pheromone and alarm response of clonal raider ant
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PMC9941220
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Insect alarm pheromones in response to predators
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Basu 2021 (WSU)
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Alarm Pheromone — ScienceDirect Topics
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Multi-phase defense by Pheidole obtusospinosa
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PMC3014660
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Colobopsis explodens
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Wikipedia
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Formica rufa
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Wikipedia
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Trap-jaw ant mandible mechanism
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J Exp Biol 226(10) jeb245396
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Ant territory formation model with alarm pheromones
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ScienceDirect S0025556425001245
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Fire ant flood raft behavior
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AMDRO
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Cadmium olfactory neurotoxicity in fire ants
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ScienceDirect S0269749124016592
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Wilson & Bossert 1963
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Theoretical framework for pheromone active space dynamics
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The Ants Chapter 7 — AntWiki
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