Sexual Conflict to the Extreme: Traumatic Insemination in Bed Bugs

Abstract

lose study of the animal kingdom uncovers a recurrent theme of a never-ending battle of the sexes. Known as sexual conflict, this struggle is characterized by contradicting optimal fitness reproduction strategies between sexes (Parker 1979, Arnqvist and Rowe 2005). What may be reproductively beneficial for one sex could potentially be costly or damaging to the opposite sex. An example of this situation occurs in the bean weevil Callosobruchus maculatus Fabricius (Fig. Males transfer tens of thousands of sperm to females during a single mating and have sharp spines on their penis that can damage the female reproductive tract and reduce female lifespan, leading to an optimal low-frequency mating strategy for females. However, males favor a high-frequency mating strategy in order to generate more offspring Another interesting case occurs in the water strider Rheumatobates rileyi Bergroth. Females of this species resist mating. Therefore almost every appendage of the male is modified for grasping the female during her resistance (Westlake et al. 2000, Arnqvist and Rowe 2005). However, the developmental rate of fifth instar males was lower than that of females while the mortality of fifth instar males was higher than that of females, suggesting that the development of the elaborate grasping traits in these male water striders is costly (Westlake and Rowe 1999, Fig.