Behaviour 2019
The Long and the Short of It: Contest Behaviours in Two Thai Stalk-Eyed Flies
Akin Heper1, Sebastian Pohl1, Jaime Grace2, Philip Johns1. 1Yale-NUS College, Singapore, , Singapore; 2Bradley University, Peoria, Illinois, United States

Stalk-eyed flies (Diopsidae) have their eyes at the ends of long eyestalks that can be sexually dimorphic and longer than body length. These flies have been model organisms for studies of sexual selection for over two decades, yet most of that research has focused on a very few species. Here we present detailed behavioural analyses of male contests for two Thai species, Teleopsis thaii and Eurydiopsis brevispinus Feijen, 1999. The first species is extremely sexually dimorphic, and the second species is sexually monomorphic, with respect to eyestalk length. We describe fight sequences between winners and losers within each species, and compare fight sequences between species. We discuss these behaviours in the context of the evolution of sexual monomorphism and dimorphism in stalk-eyed flies.