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Tropical dry forest, such as that found in Mexico, is a biome where very few alimentary resources are available during 6 months of the year. Within some families of Lepidoptera such as Nymphalidae, some species are known to survive the dry season as adults using the few decayed pulp fruits available as a food source. We compared the temporal abundance and sex ratio of two model species, one belonging to the subfamily Charaxinae, found world-wide, and one belonging to the subfamily Biblidinae, endemic to the Americas. We used baited traps to measure feeding frequency of both species to asses monthly temporal resource use curves. The butterfly frequency of feeding drops dramatically in the dry season for all species-gender, except for females of the Biblidinae species. There are few differences between the sexes in the relative feeding frequency, assimilated to activity pattern, of Charaxinae between the dry and rainy seasons, while the activity pattern of Biblidinae is very different depending on the sex. These results suggest differential consequences on mate choice competition for both species. Females of the Charaxine species showed a use curve nested on the male curve, while for all other pair-wise comparisons between gender-species, the use curves were significantly different. These differences in the temporal foraging pattern could explain at least in part, the coexistence between both sympatric species in the stressful season.

Genetic variation among 14 populations of Plutella xylostella (Linnaeus) from USA (Geneva, New York), Brazil (Brasilia), Japan (Okayama), The Philippines (Caragan de Oyo), Uzbekistan (Tashkent), France (Montpellier), Benin (Cotonou), South Africa (Johannesburg), Réunion Island (Montvert), and five localities in Australia (Adelaide, Brisbane, Mareeba, Melbourne, Sydney) were assessed by analysis of allozyme frequencies at seven polymorphic loci. Most of the populations were not in Hardy–Weinberg equilibrium and had a deficit in heterozygotes. The global differentiation among populations was estimated by the fixation index (Fst) at 0.103 for the 14 populations and at 0.047 when populations from Australia and Japan, which differed most and had a strong genetic structure, were excluded from the analysis. By contrast, the populations from Benin (West Africa) and Brazil (South America) were very similar to each other. Genetic differentiation among the populations was not correlated with geographical distance.