Abai, MR

6th International Congress of Dipterology‘Size matters!’- Mating success determined by male-tofemalesize ratio in Sepsis dissimilisPuniamoorthy, N. & R. MeierDepartment of Biological Sciences, National University of Singapore, 14 Science Drive 4,Singapore 117543.Here, I investigate the mating behaviour and morphology of Sepsisdissimilis. I describe the male courtship behaviour and use mating trials toinvestigate which male and female features determine mating success. Themating behaviour is characterized by seven very distinct male behaviouralelements (e.g., ‘hind leg curl’, ‘mid leg wave’, ‘surstylus stimulation’,‘wing flick’) and two female behaviours (‘female shake’ and ‘abdomenlowering’). There is intraspecific variation in the degree to which theseelements are displayed, but the general sequence of events remains fairlyconstant. Interestingly, most of the male behaviours are stimulatory innature and often non-contact. In order to test which morphologicalstructures influence male mating success, I measured 13 morphologicaltraits and use a principal component analysis (PCA) for analyzing the data(females: head width, scutum length, wing length; males- head width,scutum length, wing length, length of fore, mid and hind legs, length andangle of bent for longest femoral spine; length and width of the malesurstylus). I find that mating success is positively correlated with largermale-to-female size ratio rather than actual male size. None of the sexuallydimorphic features had a significant effect on mating success. The currentliterature emphasizes male traits, but my results suggest a need forconsidering female variables.Key Words: Sepsidae, sexual selection, mating behaviour, size ratio∗∗∗∗∗∗∗∗∗∗202