Eucheira socialis, commonly known as the madrone butterfly is a lepidopteran that belongs to the family Pieridae. It was first described by John O. Westwood in 1834. Locally known as Mariposa del madroño or tzauhquiocuilin, it is endemic to the highlands of Mexico, and exclusively relies on the madrone (Arbutus spp.) as a host-plant. The species is of considerable interest to lepidopterists due to gregarious nest-building in the larval stages, and heavily male-biased sex ratio. It takes an entire year for this adult butterfly to develop from an egg. The eggs are laid in the month of June and the adults emerge the following May–June. The adults have a black and white pattern on their wings, and the males are generally much smaller and paler than the females. The larvae do not undergo diapause and continue to feed and grow communally in the coldest months of the year. There are two subspecies of E. socialis, named E. socialis socialis and E. socialis westwoodi.

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