The general hypothesis tested in this thesis is whether butterfly mating strategies are affected by their life history. Several components of mating behaviour, morphological and physiological traits were studied and related to various life histories. Male and female interests are often in conflict. Males maximise their reproductive output by mating repeatedly, whereas females maximise their reproductive output by soliciting matings to obtain viable sperm and male donated nutrients, but avoiding harassment by males while searching for host plants.
Male butterflies increase their reproductive output either by delaying, or preventing, their mates from remating, because in most species the latest male to mate with a female has sperm precedence. One way in which males can delay or prevent female remating is by delivering a large spermatophore at mating. There are two ways in which males can increase ejaculate mass: 1) by growing larger - since large males produce larger ejaculates, or 2) by feeding as adults and mate at an older adult age. These two strategies are in conflict, since a larger size results from growing for a longer time as a larva. We show that large males rather than older males deliver the heaviest ejaculates. Therefore the strategy males should adopt is dependent on the mating system. In monandrous species early male emergence is especially important, since receptive females will be available during a short period. In polyandrous species it may be more beneficial to deliver large ejaculates that delay female remating; hence polyandrous males should grow for a longer time as larvae.
Males in polyandrous species deliver heavier ejaculates, and polyandrous females incorporate male donated nutrients in their eggs, and increase their reproductive output by remating. However, a comparative study of seven butterfly species failed to provide evidence that polyandrous butterfly females in general are more efficient in sequestering nitrogen from spermatophores than are monandrous females.
Stockholm: Department of Zoology, Stockholm University , 1998. , 26 p.