Amorous scorpionflies: causes and consequences of the long pairing prelude of Panorpa cognata

The scorpionfly Panorpa cognata has a prolonged premating period. After the male attracts a female, there is usually a long delay, from a few minutes to almost 7 h, before the male initiates copulation by secreting a salivary mass. In our experiments, we manipulated the amount of food, and hence the condition, of males and then measured their premating duration. The premating duration was strongly influenced by male nutrient availability and, consequently, male mating resource limitation. Males with ample resource availability, that is with large salivary glands, initiated copulations faster than males with limited resources. In addition, premating duration decreased with increasing male age. The secretion of a salivary mass was more likely to result in a successful copulation if males delayed copulation. When males initiated copulation soon after attracting a mate, nuptial gift offering often failed because of interruption by other scorpionflies or female rejection. Since the value of each invested salivary mass is high for males with limited resources, we suggest that these males invest prudently: to enhance the probability of a return on their investment, they delay secreting the salivary mass until they are confident that females are motivated to mate. Furthermore, with this strategy, males enhance the likelihood of copulating in a sheltered location, where they are unlikely to be interrupted by intruders. Alternative hypotheses are that males in poor condition have more difficulty in persuading females or that males with small salivary glands need longer to produce the salivary mass. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.