Sexual conflict and anti–aphrodisiac titre in a polyandrous butterfly: male ejaculate tailoring and absence of female control

Abstract

Males of the green-veined butterfly Pieris napi synthesize and transfer the volatile methyl salicylate (MeS) to females at mating, a substance that is emitted by non-virgin females when courted by males, curtailing courtship and decreasing the likelihood of female re-mating. The volatile is released when females display the 'mate-refusal' posture with spread wings and elevated abdomen, when courted by conspecific males. Here, we assess how the amount of MeS released by courted females changes over time since mating, and whether it is influenced by the frequency with which females display the mate-refusal posture. We also assess whether males tailor the anti-aphrodisiac content of ejaculates with respect to the expected degree of sperm competition, by comparing how males allocate MeS proportionately to first and second ejaculates in relation to ejaculate mass. The results show that females housed for 5 days in individual cages where they were able to fly and oviposit normally, released similar amounts of MeS. However, females housed together for the same period of time, causing them to frequently display the mate-refusal posture, released significantly lower levels of MeS than the individually housed females. This indicates that female display of the mate-refusal posture depletes their anti-aphrodisiac stores, and suggests that females are unable to voluntarily control their release of the anti-aphrodisiac. A comparison of relative proportion of MeS transferred by males in their first and second ejaculates showed that proportionately more MeS was allocated to the first ejaculate, in accordance with the idea that these are tailored to delay female re-mating.

Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae

“…The latter two components were present on female wings too, but in markedly lower amounts. In addition, minor male-specific components were benzyl cyanide (29), 1, and its isomer suspensolide (22), and some trace compounds of unknown identity.…”

“…Males transfer volatile compounds-socalled antiaphrodisiacs-onto the females during copulation; these render them unattractive for other males. Methyl salicylate was identified as an antiaphrodisiac of P. napi, [21,22] while the related P. rapae uses both methyl salicylate and indole (26). In P. brassicae benzyl cyanide (29) serves this function.…”

Courtship behavior of Heliconius erato phyllis (Lepidoptera, Nymphalidae) towards virgin and mated females: conflict between attraction and repulsion signals?

“…This pheromone may have acquired a double function from the moment when it started to be transferred to females, decreasing the likelihood of remating and, subsequently, minimizing the time spent in courtship with mated females for both sexes. Besides Heliconius, the use of antiaphrodisiacs in Lepidoptera has been reported only for the Pieridae family (Andersson et al 2000(Andersson et al , 2003(Andersson et al , 2004 where, differently from Heliconius, the repulsive substance drains after some days in females and they return to mating.…”

Potential for CFC in Black Widows (Genus Latrodectus): Mechanisms and Social Context

“…In a laboratory study, females that consumed their first mate during and after their second copulation were less likely to copulate with a subsequent male compared to females that did not cannibalize their first mate ( 10 Andrade 1996). This result has not been replicated, however, and it is unclear whether such an effect might arise as a female decision or via chemical manipulation by males (e.g., Andersson et al 2004;Aisenberg and Costa 2005), particularly since cannibalistic matings are longer and thus may include the transfer of more ejaculatory substances. Chemical manipulation is not likely to explain premature cannibalism, however, as males are often wrapped in silk and disabled, but not consumed by females when attacked during the inter-copulatory interval.…”