Gray Hairstreak (Strymon melinus) is a small butterfly, with a wingspan of 0.875 to 1.375 inches. In our local area, it can be seen from March to October. Numbers peak in August. There is a large variety of host plants, most often from the pea (Fabaceae) and mallow (Malvaceae) families, including beans (Phaseolus), clovers (Trifolium), and mallows (Malva).
Hairstreaks are named for the thin tails, which are part of an elaborate defense mechanism. The tails mimic antennae, and the eye-spots mimic eyes. When the butterfly rubs its hindwings together to draw attention to this false head (see video), predators are fooled into thinking the tail is the head. The predator strikes there; the butterfly loses only a bit of wing, and flies away (butterflies are able to fly normally even with large chunks of wing missing).
Like Acmon Blue, Gray Hairstreak has a mutualistic relationship with ants (both species benefit). The ants protect the caterpillars from predators in exchange for the sweet “honeydew” the caterpillars secrete from a nectary gland. Roughly three-fourths of butterflies in the Lycaenidae family have a relationship with ants, but not always mutualistic.
It is found along the southern edge of Canada, all across the US and Mexico and Central America, into the northern edge of South America.
