Asymmetric genitalia in insects and spiders
(Published in Biological Reviews, 2007; together with B. Sinclair and M. Schmitt; PDF)
After doing some work on asymmetric genitalia in pholcid spiders (papers on Metagonia mariguitarensis and Kaliana [now Mesabolivar] yuruani), I was wondering why asymmetric genitalia are so rare in spiders but so widespread in insects. I was surprised to find that no review on insect genital asymmetries has been written for over 70 years, so I spent several months digging for hundreds of papers on insect gentalia, mating positions, genital mechanics, and insect relationships. The resulting story is fairly complex, but it all seems to boil down to one fundamental difference between insects and spiders: the unpaired versus paired male copulatory organs.
A short summary has been published in Genetica (2010; PDF).


Dorsal views of genitalia of two closely related species, one symmetric (left: Poecilopsyche pandu, Trichoptera), the other asymmetric (right: P. durdhyodhana); projections of tenth segment in grey (from Schmid, 1968).