Potential influence of insect lifestyles on the cuticular profile: A comparative study on social, solitary and parasitic Halictinae (Hymenoptera, Halictidae)
Chemicals on the cuticle are used for communication in a wide range of insects. The insects expose different chemical substances (mainly hydrocarbons, but also polar substances) on their surface that carry information about their sex, their reproductive status and further more. Con- or heterospecific insects can detect the chemical profile with their antennae and “read” the information.
Solitary hymenopteran species can deal without most of intraspecific communication from female to female. They predominantly have to find a mate for reproduction and have to detect intruders, which e.g. want to take over their nest, and drive those intruders away.
In contrast, social Hymenoptera live together in one nest with several closely related conspecific individuals. To facilitate this lifestyle, the individuals have to be able to distinguish between nestmates and non-nestmates, to communicate reproductive status etc. Our question on that is, whether solitary species have less complex cuticular profiles than social ones, because they do not need to communicate so much with other females of their species.
Another type of lifestyle is living as a brood parasite. Their main goal is to enter a host’s nest for oviposition without being detected. Therefore, they should not leave chemical marks that reveal their presence in the hosts nest. To achieve that they could be completely lacking noticeable substances or be just invisible for their host by having almost the same chemical profile as the host. This is chemical mimicry and our question is, whether we can find it in a brood parasite.
Since hymenopteran males do not participate in the same tasks as females, differences in lifestyle that affect solely females should not play a major role in shaping the males’ chemical profile. This leads us to the following questions: Do males have less complex profiles than females? Are there bigger differences between males and females in social species than in solitary ones, because the need for communication is more similar in males and females of solitary species but bigger in social females than in males of a social species?
A very good model for answering our questions is the subfamily of Halictinae, a group of bees with worldwide distribution. Interestingly, within the genera Halictus and Lasioglossum, there are primitively eusocial species, primarily solitary species and species which reversed from sociality to being solitary. A third genus of Halictinae is Sphecodes, whose species are obligate brood parasites on other bee species, mostly Lasioglossum, Halictus and Andrena (Hymenoptera: Andrenidae). For this study, we compare the chemical profiles of various species of these genera with respect to their different lifestyles.
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