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ItemCuticular hydrocarbon mimicry of the ant Oecophylla smaragdina by the salticid spider Cosmophasis bitaeniata(University of Melbourne, 1998)Social insects use cuticular hydrocarbons to differentiate between species, but the evidence that cuticular hydrocarbons are used to differentiate between non-nestmate conspecifics is inconclusive. The salticid spider Cosmophasis bitaeniata is a myrmecophile that lives within and on the arboreal nests of the green tree ant Oecophylla smaragdina. Remarkably this spider preys on the larvae of its highly territorial and aggressive host. Gas chromatography and mass spectrometry reveal that C. bitaeniata mimics the cuticular hydrocarbons of O. smaragdina. Recognition bioassays involving the extraction of cuticular hydrocarbons from ants and spiders, the transfer of these substances to discs of filter paper, and the behavioural response of foraging major workers, reveal that the cuticular hydrocarbons of spiders appear to be chemically �invisible� to foraging major workers. While the cuticular extracts of non-nestmate workers are attacked by foraging workers, those of nestmates are given attention that is not aggressive. These data together with additional bioassays reveal that the qualitative chemical resemblance of ants by spiders, combined with the spiders ability to avoid contact with major workers, function to avoid detection by major workers of O. smaragdina. The relative proportions of the cuticular hydrocarbons of social insects may constitute a colony recognition cue that workers use to differentiate between nestmate and non-nestmate conspecifics. Hydrocarbon proportions are also used to differentiate between different castes within a species. The relative proportions of the cuticular hydrocarbons of spiders are colony-specific, with the variation in the hydrocarbon proportions of spiders within a colony being less than the variation in hydrocarbon proportions between colonies. Major workers of O. smaragdina also have colony-specific cuticular hydrocarbon proportions. However, these proportions are not mimicked by spiders. This suggests that spiders may mimic either the minor workers or the larvae of their hosts. Recognition bioassays involving the capture of larvae in the presence of major and minor workers and the behaviour of ants and spiders when combined with nestmates and non-nestmates were conducted. These bioassays revealed that colony-specific cuticular hydrocarbon mimicry may function more to obtain prey from minor workers than to avoid eliciting aggression from nestmate major workers. These data also suggest that cuticular hydrocarbon proportions are used as colony recognition cues in ants. Myrmecophiles may obtain their mimetic cuticular hydrocarbons either directly from their host via direct contact or by biosynthesising them. Experiments reveal that C. bitaeniata avoids contact with workers, does not lose its mimetic hydrocarbons when isolated from workers, and does not biosynthesise its cuticular hydrocarbons. Additional experiments involving raising spiderlings on artificial diets reveal that the mimetic hydrocarbons of spiders are acquired by consuming the larvae of O. smaragdina. These data suggest that dietary acquired hydrocarbons can be transferred directly to the cuticle of spiders, via the haemolymph. Furthermore, the spiders have colony-specific hydrocarbon proportions if they eat the larvae from a single colony of O. smaragdina. The larvae of O. smaragdina also possess cuticular hydrocarbon proportions that are colony-specific. These data suggest that spiders chemically mimic the cuticular hydrocarbons of the larvae of their host.