False heads and sexual behaviour in a hairstreak butterfly, Callophrys xami (Lepidoptera: Lycaenidae)

In several butterfl ies, the posterior end of the hindwings resembles a butterfl y head when the butterfl y is perched with its wings closed. There is evidence that this “false head” (FH) defl ects predator attacks towards non-vital parts of the body. If the FH protects from visually oriented predators, its condition in an individual butterfl y could provide information about its quality to prospective mates. We tested two hypotheses based on this idea by comparing the probability of mating, duration of copulation and size of the ejaculate received by females of Callophrys xami (Lycaenidae) with an intact FH and those with an ablated FH in a paired experiment. The absence of a FH had no effect on the probability of mating, but females with an ablated FH copulated for longer and received larger ejaculates, which supports the hypothesis that males prefer females with damaged FHs because this reveals the female’s ability to defl ect attacks. Male or female (or both) cryptic choice could also account for our results, but more studies are needed to test this. * Corresponding author; e-mail: cordero@ecologia.unam.mx INTRODUCTION Deception is widespread in nature (Wickler, 1968; Ruxton et al., 2004; Howse, 2014; Stevens, 2016). In several species, some individuals provide misleading information that results in fi tness benefi ts for them and fi tness costs for the “tricked” organisms (Ruxton et al., 2014; Stevens, 2016). A classic example of deception is the “false head” present in many butterfl y species of the family Lycaenidae (Robbins, 1980). In these species, the posterior end of the hindwings resembles the head of a butterfl y that is perching with its wings closed. This resemblance is reinforced by specifi c behaviour, such as the back and forth movement of the hindwings that helps the hindwings tails (the “false antennae”) simulate the movements of real antennae (López-Palafox et al., 2015). This false head (FH hereafter) is explained as an adaptation that defl ects attacks from predators to non-vital parts of the body (Robbins, 1980; Cordero, 2001). There are only two experimental tests of this idea using species of Lycaenidae (Sourakov, 2013; López Palafox & Cordero, 2017), and in one case the results were inconsistent with the hypothesis (López Palafox & Cordero, 2017). However, comparative data on failed predator attacks on the hindwings support the predictions Eur. J. Entomol. 118: 394–398, 2021 doi: 10.14411/eje.2021.040