Other Common Names
Common Hairstreak, cotton square borer (caterpillar)
Synonyms and other taxonomic changes
First described in 1818 by Jacob Hübner
as Strymon melinus
Explanation of Names
Probably from Greek melinos (μελινος)- "ashen"
Wingspan: 7/8 - 1 3/8 inches (2.2 - 3.5 cm).
One tail on hindwing. Upperside blue-gray with large red spot near tail. Underside of spring/fall form is dark gray, summer form is paler gray. Relatively straight postmedian line is white, bordered with orange on the inside edge. Usually an orange patch at back of head, and males most often have orange abdomens.
Caterpillar is variably green, has long hairs on dorsum, fairly distinctive in this family (1)
Throughout continental United States from southern Canada south to Mexico; southward to Venezuela.
Open, nonforested sites; common in disturbed, weedy areas.
Two flights from May-September in the north, three-four flights from February-November in the south.
Caterpillar hosts: Flowers and fruits from an almost endless variety of (usually) herbaceous plants; most often from pea (Fabaceae) and mallow (Malvaceae) families including beans (Phaseolus), clovers (Trifolium), cotton (Gossypium), and mallow (Malva).
Adult food: Nectar from many flower species including dogbane, milkweed, mint, winter cress, goldenrod, tick trefoil, and white sweet clover.
Males perch all afternoon on small trees and shrubs to seek receptive females. Eggs are laid singly on flowers of host plant. Young caterpillars feed on flowers and fruits; older ones may eat leaves. Caterpillars are sometimes attended by ants, which receive a sugary solution from the dorsal nectary organ (Idaho Museum of Natural History, (2)
, BugGuide photos). Chrysalids hibernate (1) (3)
Caterpillar with attendant ant, larva inside pole bean, larva, pupa, emerged adult
The most widespread hairstreak in North America.
Wagner, p. 103, illustrates larva (1)
Allen, pp. 99-100, plate 10--imago, 34--larva, 46--pupa (2)
Scott, #358, gives extensive list of hostplants (3)
Idaho Museum of Natural History, Digital Atlas of Idaho
, species account for Gray Hairstreak
--mentions association with ants
Zuträge zur Sammlung exotischer Schmettlinge, p.22
Hübner's original description of the species (in German, with Fraktur