Spring Azure

Celastrina ladon — the spring azure — is one of the most familiar small butterflies in eastern North America and a flagship species in studies of MYRMECOPHILY (ant-tended) butterfly biology. The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to northern Florida and west to the Great Plains. Adults are 2-3 cm wingspan with brilliant SKY-BLUE wings (uppersides) and pale blue-gray undersides marked by small dark spots. The brilliant blue coloration is created by STRUCTURAL COLORATION — microscopic wing scale ridges that scatter blue light through interference (the same mechanism that creates the blue color in morpho butterflies and peacock feathers — the wings contain no blue pigment, only colorless ridges). The blue is one of the brightest blues in any North American butterfly. The species is one of the EARLIEST-EMERGING butterflies in eastern NA — adults can appear as early as March in the southeastern US (well before most NA butterflies emerge for the spring), and the appearance of spring azures fluttering through still-leafless deciduous forest is one of the cultural icons of late-winter/early-spring in eastern NA natural history. The species is one of the most-cited examples of MYRMECOPHILY (ant-tended biology) in butterfly biology. SPRING AZURE LARVAE PRODUCE SWEET HONEYDEW SECRETIONS from specialized abdominal glands (the 'dorsal nectary organ'), and this honeydew attracts ATTENDING ANTS — primarily Camponotus (carpenter ants) and Crematogaster (acrobat ants) species. The ants drink the honeydew and in return PROTECT the caterpillar from parasitoid wasps and predatory spiders by aggressively attacking any small arthropod that approaches the caterpillar. The mutualistic relationship is one of the most-studied butterfly-ant mutualisms and is a flagship case study in lycaenid (family Lycaenidae) biology. Most lycaenid butterflies have some degree of myrmecophily — Lycaenidae includes the 'blues' (Celastrina, Lycaeides, etc.), the 'coppers' (Lycaena), the 'hairstreaks' (Satyrium, etc.), and the most extreme myrmecophiles (the 'large blue' Phengaris arion and related species, which have larvae that are CARRIED INTO ANT NESTS and feed on ant larvae as obligate ant-nest parasitoids). Spring azure larvae feed on a wide range of woody plant flowers (especially flowering dogwood, viburnum, blueberry, cherry, and meadowsweet) — the larvae consume flower buds and developing fruits rather than leaves, and the host plants must be in FLOWERING state for larvae to develop. The species is harmless to humans and a major beneficial pollinator (and food source for tending ants).