In the United States, there are currently 15 lycaenid butterfly species listed under the Endangered Species Act. As pesticide toxicity testing cannot be easily conducted with listed species, there is a need to identify non-target lycaenid species that can serve as surrogates for their listed counterparts. These non-target lycaenids should have similar characteristics and be widely accessible and relatively easy to rear and manipulate under laboratory conditions. Currently, there are no published rearing methods or life cycle data for such species; we therefore present this information for eastern tailed-blue butterflies (Lycaenidae: Cupido comyntas), which have a vast range across the country, are abundant, and feed on a variety of common plants, including clover (Fabaceae: Trifolium spp.). We developed successful laboratory rearing methods for the species, estimated the number of larval instars and leaf consumption rate, and obtained weights, surface areas, and developmental days for the various life stages (larval instars, pupae, and adults). We found the lab-reared adults to be significantly smaller than the wild-caught adults, consistent with patterns reported for some other butterfly species. The eastern tailed-blues also had similar life cycle characteristics to most listed lycaenids, and we successfully employed them in preliminary pesticide toxicity bioassays. Overall, our data supports the use of the eastern tailed-blue as a promising surrogate for listed lycaenid species, particularly for generation of pesticide toxicity data.