The Blow Fly Waltz: Field and Laboratory Observations of Novel and Complex Dipteran Courtship Behavior

Complex courtship has been well documented in the Diptera. However, studies have focused on a limited number of taxa and mostly using lab populations, where behavior can differ substantially compared to nature. To broaden our understanding of dipteran courtship, studies are required in a wider range of species, across both wild and captive populations. The blow flies (Diptera: Calliphoridae) include some of the most commonly encountered flies, yet courtship has been documented in less than 1% of species and is reported to be brief and simple throughout the family. To further investigate blow fly courtship, and to assess the effect of captivity on behavior, this study aimed to document the courtship of a habitat specialist that is endemic to Australasia, Chrysomya flavifrons. Video footage of wild and captive groups was recorded and analyzed using behavioral analysis software. The specific aims were 1) to quantify the behavioral sequences that constitute courtship and 2) to compare courtship between wild and captive flies. We found that the courtship behavior of Ch. flavifrons was complex and stereotyped, consisting of five discrete behaviors, which starkly contrasts with the simple courtship observed in most calliphorids. All of these stereotyped behaviors were observed in both wild and captive groups. However, the proportion of time males spent on these behaviors differed substantially. These findings highlight that blow fly courtship behavior may be more complex than currently perceived, and that careful consideration should be given to the influence of the laboratory environment in future studies of fly behavior.