Leg size affects male mating success in Tarsonemus confusus ewing (Prostigmata: Tarsonemidae)

Abstract

Legs IV of males in the family Tarsonemidae are highly modified to form thickened pincer-like appendages. Previous literature describes males using legs IV both to manipulate pharate females onto the males genital capsule as well as to constrain the adult female s legs during mating. We observed behavioural interactions between males and females from three populations of Tarsonemus confusus Ewing. We did not witness males using legs IV in the reported manner, but rather saw them using legs IV in contests for possession of pharate females. Male body size and leg IV size were positively correlated for the three populations of T. confusus. However, the correlation was imperfect and males of the same body size often had different leg sizes. When two males were placed into an arena with a pharate female, the male that succeeded in capturing and guarding the female had legs IV that were significantly longer and larger (by area) than those of the loser. However, there was no significant difference in body size between the successful and unsuccessful males.