Body Odor and Sex: Do Cuticular Hydrocarbons Facilitate Sexual Attraction in the Small Hairy Maggot Blowfly?

Abstract

Cuticular hydrocarbons (CHCs) play an important role as contact pheromones in insects, particularly in flies. However, for many fly taxa our understanding of the importance of CHCs in sexual communication is limited. Within the family Calliphoridae (blowflies), sex-specific differences in CHCs have been reported for several species, but there is no evidence that CHCs facilitate sexual behavior. In order to elucidate the function of CHCs in Calliphoridae, studies combining behavioral and chemical analyses are required. The present study used gas chromatography/mass spectrometry, along with behavioral assays, to assess whether CHCs facilitate sexual attraction in the small hairy maggot blowfly, Chrysomya varipes. The specific aims were to: 1) determine if CHCs differ between the sexes and 2) assess whether flies exhibit positive chemotaxis to CHCs of the opposite sex. Fifty-two hydrocarbons common to both sexes were identified, and quantitative differences for numerous CHCs were observed between the sexes. However, behavioral assays provided no evidence that flies were attracted to CHCs of the opposite sex, challenging the hypothesis that CHCs facilitate sexual attraction in Ch. varipes. In contrast to other blowflies, Ch. varipes males invest heavily in courtship displays and ornamentation, so we speculate that visual communication in this species may have relaxed sexual selection for chemical communication. More broadly, our findings support suggestions that CHCs may not always facilitate insect sexual communication.

The evolution of sexually dimorphic cuticular hydrocarbons in blowflies (Diptera: Calliphoridae)

“…Broadly, the monomethylalkanes, n ‐alkenes and n ‐alkanes predominated the cuticular profiles of most species, which aligns with previous reports of blowfly CHCs ( L. cuprina : Barbosa et al., 2017; Ch. varipes : Butterworth, Byrne, Keller, & Wallman, 2018; Ch. rufifacies : Pechal et al., 2014; and Ch.…”

“…In these two species, selection on CHCs as sex‐specific cues may have been relaxed or replaced by other compounds or signalling modalities—as appears to be the case in Ch. varipes (Butterworth et al., 2018). Nevertheless, even in species where sexual dimorphisms were not clear, CHCs may still be important for conspecific recognition, as is evident in the blowfly Phormia regina (Stoffolano et al, 1997), or for the recognition of sexual maturity (Butterworth et al., 2020).…”

“…Notably, previous work has found CHC profiles to be sexually dimorphic in laboratory populations of Ch. varipes (Butterworth et al., 2018). However, we did not observe this in the wild populations.…”

“…flavifrons is a habitat specialist, restricted to the rainforests of Northern New South Wales and Queensland (Butterworth et al., 2019), whereas Ch. varipes is a habitat generalist, which is broadly distributed across the Australian continent (Butterworth et al., 2018). These extreme differences in habitat have likely led to divergent pressures on CHC expression for desiccation resistance, which may explain the increased proportions of n ‐alkenes and n ‐alkanes in Ch.…”

Behavioural response of Lucilia sericata to a decaying body infested by necrophagous insects

“…To evaluate the ability of L. sericata to discriminate between the odour of different corpse (colonized or not by necrophagous insects), a choice arena was set up in a large Petri dish (diameter 20 cm, height 4 cm) (Butterworth et al ., ). The dish was divided into quarters, each associated with one of the four different VOC source (rats with no insect, rats with L. sericata , rats with D. frischii and rats with both L. sericata and D. frischii ).…”