Experimental manipulation of male behaviour during copulation in Stenomacra marginella (Heteroptera: Largidae):: Effect on copula duration, female remating and oviposition

Apparently stimulatory male copulatory behaviour (MCB) is widespread among arthropods and it could help males to increase their fitness by inducing favourable behavioural and physiological changes in females. The empirical study of female responses to MCB is hindered because its experimental manipulation is difficult. We have developed a technique for reducing, with minimal disturbance, the frequency of MCB in the true bug Stenomacra marginella. Here, we test the idea that, in a polygamous species like S. marginella, sexual selection favours males whose MCB induces females to increase copula duration (thereby increasing the amount of sperm and accessory substances transferred), reduce their sexual receptivity to additional males and increase their rate of oviposition. Males prevented from performing MCB increased their rate of attempts to perform MCB. Copulations with previously mated females were of longer duration than those with virgin females, probably as a male adaptation for sperm competition, and MCB could have played a role in inducing this effect. Partial or total experimental reduction of MCB frequency had no effect on remating rates, because most females accepted remating at the first opportunity (I day after their first copula). The probability of egg laying was reduced in females whose first mate was partially prevented from performing copulatory courtship, but not in females whose first mate was completely prevented from performing copulatory courtship. This is an intriguing result and further experiments are needed to understand its causes. We hypothesize that MCB evolved as a result of sexual selection. (c) 2006 Elsevier B.V. All rights reserved.