Strategic Variation in Male Courtship Persistence in the Butterfly Eurema hecabe

The males of many insect species have experienced intense sexual selection for the ability to swiftly locate sexually receptive females. This is thought to have engendered the evolution of highly efficient mate location strategies, and to favour flexibility in male behaviour as commensurate with the potential net payoff in terms of securing a mate. In the common grass yellow butterfly (Eurema hecabe), males visually search for receptive females by patrolling in and around patches of the larval host plant. Females of this weakly polyandrous species are sexually receptive immediately upon eclosion, and then once or possibly twice during adulthood. For the males, the likelihood of achieving copulation is very high when they encounter a newly eclosed, immobile female, but low when they approach older, pre-mated females, who are generally seeking to oviposit. Here we show that E. hecabe males optimise their chances of copulation by allocating their mate search efforts according to the likely availability of receptive females. Males engage in a dedicated search for freshly emerged (teneral) females around the peak time of pupal eclosion (early morning) then shift to lengthier courtships of older, flying females (late morning). The males appear to continue the search for teneral matings alongside the courting of mature females in the late mornings, so the primary behavioural shift concerns the length of time males are willing to invest in courting flying females. These findings support the general expectation for flexibility in male search tactics as a function of female receptivity.