Recently I’ve been seeing occasional little blue butterflies fluttering around the margins of a forest in southeast Michigan. I finally found one that would hold still long enough to be photographed. It’s one of several species of azure butterflies (Celastrina sp., Lycaenidae). While the markings on the lower sides of the wings seem distinct, they’re not enough to distinguish the species. I wish I could have photographed the upper sides of the wings, because they were strikingly blue.
In addition to the notable coloration of the adults, the larvae of many (if not all) Celastrina species have an interesting mutualism with ants known as myrmecophily. Larvae secrete a sweet substance known as honeydew that attracts ants. Ants often attend to the caterpillars to protect this prized food. In such an arrangement the ants benefit from a reliable, high-quality food source, while the butterfly larvae benefit from the protection offered by the ants.