Lack of evidence that the false head of male Callophrys xami (Reakirt, 1867) (Lepidoptera, Lycaenidae) is a sexually selected trait

Colourful and morphologically complex traits can be used to deflect predators’ attacks to a part of a prey’s body that is less vulnerable. This is the case of the so-called false head (FH) of some butterfly species, in which the posterior end of the hindwings of individuals perching with closed wings resembles a butterfly’s head. Recently, it was shown that the FH of Callophrys xami (Reakirt, 1867) females also plays a role in sexual selection. Specifically, females with an experimentally ablated FH received larger ejaculates, suggesting that males exert postcopulatory (cryptic) choice in favour of these females, perhaps because they have shown to be able to deflect predator attacks. Here, we tested experimentally whether C. xami females also show a preference for males with ablated FH. In our paired experiment, we presented virgin females either with a male with the FH ablated or with a male with the FH intact. We compared the probability of mating, copula duration and the number of eggs laid by the females two days after mating. We did not find evidence of female choice in relation to the presence/absence of FH in the males. Males with ablated FH were as likely to mate as control males. Copula duration and number of eggs laid were also very similar in females mated with either males with the FH ablated or intact. We suggest that the structure of the courtship behaviour of this butterfly could explain why males use the FH in their choice of mate, while females apparently do not.