Average total cyanogenic compounds content in virgin and mated Z. filipendulae adults as well as in discarded males (which females would not mate with). Error bars are standard deviation. (figure modified from Zagrobelny et al. 2007).The researchers then compared the cyanogenic compounds of virgin males and females, as well as mated males and females they paired up in the laboratory (see figure above). Virgin males and females had roughly similar levels of cyanogenic compounds. In contrast, after mating, females had larger levels, whereas males had lower levels. This indicates that during mating, males transfer some of these chemicals to the female, likely with the sperm. The levels of cyanogenic compounds in rejected males (males in an experimental pair that the females refused to mate with) were lower than average levels in virgin males, which suggests that females will mate preferentially with those males better loaded with chemical weapons. Why would the female benefit from acquiring more cyanide compounds. Possibly because the more she puts into eggs, the better defended they will be from predators, so this nuptial gift might be seen as a form of paternal behaviour. Alternatively, the female might gain through using this nuptial gift to produce more pheromone, attract further males and increase the vigour of her offspring.
A Six-Spot Burnet on Bird's Foot TrefoilReferences
Zagrobelny M, Bak S, Olsen CE, & Møller BL (2007). Intimate roles for cyanogenic glucosides in the life cycle of Zygaena filipendulae (Lepidoptera, Zygaenidae). Insect biochemistry and molecular biology, 37 (11), 1189-97 PMID: 17916505