Robert K. Vander Meer

Direct Behavioral Evidence for Hydrocarbons as Ant Recognition Discriminators

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Chemical Mimicry in the Myrmecophilous Beetle Myrmecaphodius excavaticollis.

The myrmecophilus beetle Myrmecaphodius excavaticollis (Blanchard) was found to have species-specific cuticular hydrocarbons acquired-from one of its hosts, the ant Solenopsis richteri Forel. Removal from its ant host resulted in loss of the host hydrocarbons, leaving a cuticular pattern innate to the beetle. When beetles were transferred to colonies of three other Solenopsis species, they acquired the specific hydrocarbons associated with each of the new hosts. This passive integration mechanism is coupled with the beetles armored exterior to enable it to cope with multiple aggressive hosts.

Temporal changes in colony cuticular hydrocarbon patterns ofSolenopsis invicta

Heritable cuticular hydrocarbon patterns ofSolenopsis invicta workers are consistent within colonies for a given sampling time but vary sufficiently from colony to colony to distinguish the colonies from each other. In addition, cuticular hydrocarbon patterns change within colonies over time. Nestmate recognition cues found on the individuals cuticle, can be from heritable or environmental sources, and are a subset of colony odor. The cuticular hydrocarbons can be used as a model for heritable nestmate recognition cues. We propose that because potential nestmate recognition cues, both environmental and genetic, are dynamic in nature rather than static, during its lifetime a worker must continually update its perception (template) of colony odor and nestmate recognition cues.

Ontogeny of nestmate recognition cues in the red carpenter ant (Camponotus floridanus): Behavioral and chemical evidence for the role of age and social experience

SummaryA combination of behavioral and chemical analyses was used to investigate the nature of nestmate recognition cues and the effects of worker age and social experience on these cues in the ant Camponotus floridanus. Five categories of workers were tested: foragers, 5-day old and 0-day old callows, 5-day old and 0-day old naive callows. Bioassays consisted of introductions of dead workers from these categories into their own colonies or into an alien colony after the following treatments: 1) killed by freezing, 2) solvent-washed, 3) solvent-washed and coated with a nestmate soak, 4) solvent-washed and coated with a non-nestmate soak. Soaks were obtained from individual ants immersed in hexane and were applied individually to washed workers from the same category. Soaks were analyzed by gas chromatography (GC) and compared by multivariate analyses. Freeze-killed workers from each category elicited more aggressive behavior in the alien colony than in its own. By comparing GC profiles, a worker from any category can be assigned to its colony of origin. Thus all studied worker categories are colony-specific. Solvent-washed ants did not induce more aggressive behaviors in the alien colony than in their own, but they induced significantly less aggressivity in an alien colony than non-treated dead ants from the same category. Washed ants indced more aggressive behaviors when coated with a soak from a different colony as opposed to a soak from the colony in which they were introduced. The combination of behavioral and chemical results lead to the following conclusions: 1) Information contained in soak derived from workers was sufficient to allow nestmate recognition. 2) Nestmate recognition cues, and consequently the recognition response displayed to their bearer, change with age. 3) Social experience is necessary to develop or acquire a colony-specific label. The role of age and social experience on nestmate recognition in social Hymenoptera is discussed.

Octopamine modulates honey bee dance behavior

Honey bees communicate the location and desirability of valuable forage sites to their nestmates through an elaborate, symbolic “dance language.” The dance language is a uniquely complex communication system in invertebrates, and the neural mechanisms that generate dances are largely unknown. Here we show that treatments with controlled doses of the biogenic amine neuromodulator octopamine selectively increased the reporting of resource value in dances by forager bees. Oral and topical octopamine treatments modulated aspects of dances related to resource profitability in a dose-dependent manner. Dances for pollen and sucrose responded similarly to octopamine treatment, and these effects were eliminated by treatment with the octopamine antagonist mianserin. We propose that octopamine modulates the representation of floral rewards in dances by changing the processing of reward in the honey bee brain. Octopamine is known to modulate appetitive behavior in a range of solitary insects; the role of octopamine in dance provides an example of how neural substrates can be adapted for new behavioral innovations in the process of social evolution.

Chemical mimicry in a parasitoid (Hymenoptera : Eucharitidae) of fire ants (Hymenoptera : Formicidae)

A wasp (Orasema sp.) parasitic on the fire ant,Solenopsis invicta Buren, develops to the adult stage within the ant colony, where wasp larvae are ectoparasitic on ant pupae. This phase of the parasites life cycle requires a mechanism of integration into the host colony. Gas Chromatographic profiles of hexane soaks of various stages of the parasite and host suggest that during development within the ant colony the parasite acquires the colony odor of the host through a passive mechanism, based on simple contact and other social interactions. No parasite-specific components were observed. After leaving the host nest as adults, the parasite biosynthesizes a parasite-specific cuticular compound, while retaining residual amounts of the host acquired components. This complicated scenario is consistent with current knowledge of nestmate recognition and the preferential treatment of ant workers to their brood.

Gaster flagging by fire ants (Solenopsis spp.): Functional significance of venom dispersal behavior.

Behavioral and chemical studies with laboratory colonies indicate that the imported fire antSolenopsis invicta Buren (Myrmicinae) disperses venom through the air by raising and vibrating its gaster (i.e., “gaster flagging”). This mechanism of airborne venom dispersal is unreported for any ant species. Foraging workers utilize this air-dispersed venom (up to 500 ng) to repel heterospecifics encountered in the foraging arena, while brood tenders dispense smaller quantities (∼ 1 ng) to the brood surface, presumably as an antibiotic. Brood tenders removed from the brood cell and tested in heteropspecific encounters in the foraging arena exhibited the complete repertoire of agonistic gaster flagging behavior. These observations suggest that airborne venom dispersal by workers is context specific rather than temporal caste specific and that workers can control the quantity of venom released.

Queen primer pheromone affects conspecific fire ant (Solenopsis invicta) aggression

Abstract. Monogyne fire ant, Solenopsis invicta, colony workers are territorial and are aggressive toward members of other fire ant colonies. In contrast, polygyne colony workers are not aggressive toward non-nestmates, presumably due to broader exposure to heritable and environmentally derived nestmate recognition cues (broad template). Workers from both monogyne and polygyne fire ant colonies execute newly mated queens after mating flights. We discovered that monogyne and polygyne queens have a remarkable effect on conspecific recognition. After removal of their colony queen, monogyne worker aggression toward non-nestmate conspecifics quickly drops to merely investigative levels; however, heterospecific recognition/aggression remains high. Queenless monogyne or polygyne worker groups were also not aggressive toward newly mated queens. Queenless worker groups of both forms that adopted a monogyne-derived newly mated queen became aggressive toward non-nestmate workers and newly mated queens. We propose that the powerful effect of fire ant queens on conspecific nestmate recognition is caused by a queen-produced recognition primer pheromone that increases the sensitivity of workers to subtle quantitative differences in nestmate recognition cues. This primer pheromone prevents the adoption of newly mated queens (regulation of reproductive competition) in S. invicta and when absent allows queenless workers to adopt a new queen readily. This extraordinary discovery has broad implications regarding monogyne and polygyne colony and population dynamics.

Sources of nestmate recognition cues in the imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae)

Abstract Aggression bioassays were conducted to investigate nestmate (worker-worker) recognition in monogyne colonies of the imported fire ant. Environmentally correlated cues dominated the recognition cue hierarchy of laboratory and field colonies, anddiet alone significantly modified recognition labels and templates of laboratory-reared workers. ‘Discriminators’ associated with worker genotype also affected recognition, but ‘queen discriminators’ did not significantly affect either labels or templates of laboratoryreared workers exposed as adults to alien queens for 28 days. Factors contributing to the importance of environmentally derived recognition cues in this species and the potential implications of such cues for the formation of polygynous fire ant populations are discussed.

Isolation of the trail recruitment pheromone ofSolenopsis invicta.

TheSolenopsis invicta trail pheromone is synthesized by the Dufours gland and is released through the sting apparatus. The recruitment subcategory of theS. invicta trail pheromone was shown to be composed of a mixture of the orientation pheromone, (Z,E)-α-farnesene and an unidentified homosesquiterpene consisting of three rings and one double bond (C-1). C-1 is present in worker Dufours glands at only 75 pg per worker equivalent. This is the first report that demonstrates that different exocrine products from the same gland control different subcategories of behavior related to mass recruitment.