Alabama Butterfly Atlas

Edwards' Hairstreaks have one brood, flying once a year in early summer.  The flight typically coincides with the blooming of Butterfly Milkweed, a favorite nectar source.  Other nectar sources are also used, but Butterfly Milkweed is a magnet.  Both sexes avidly nectar and often sit together on the same flower head. Males perch on low vegetation (or even the ground) to establish territories and to look for females; they are very noticeable when they dart out to investigate anything that flies. 

Females deposit eggs in bark crevices on sapling trees. In Alabama, tree height has been documented to range from 10 feet to 12 inches, with most topping out at 2 feet or less. Placement is low on the tree trunk, sometimes at ground level. Several eggs may be placed in one spot, where they remain throughout the fall and winter. In spring, caterpillars hatch and eat young leaves.  At third instar, larvae develop a honey gland (sometimes called a Newcomer’s organ) that secretes a sugary substance extremely attractive to ants. A species of wood ant (Formica integra) discovers the caterpillars and defends them against predators in order to protect their food source.  The ants build a detritus structure known as a byre at the foot of the caterpillars’ host tree.  During the day, caterpillars rest/hide within the byre.  Under cover of darkness, they journey up the tree to eat. Ants precede them and sweep the area for predators. At dawn, the caterpillars, along with attendant ants, crawl back down the tree to the shelter.  Chrysalides are formed within the byre, in ant tunnels within or under the byre, in nearby dead leaves, or are attached to the host tree's base. Since Edwards’ Hairstreak pupae also contain Hinton’s glands, ants continue to vigorously defend them.  Upon emergence, adult hairstreaks crawl out of subterranean chambers if their chrysalides were formed within the ants’ tunnels.

Edwards’ Hairstreaks’ close resemblance to other hairstreaks in their genus (satyrium) and their short flight time makes them easy to overlook and misidentify. Prior to 2020, Edwards’ Hairstreaks were known from only two sites in Alabama. In late May of that year, an Edwards' was identified in a photograph from the Shoal Creek Ranger District of the Talladega National Forest. In the three weeks that followed, there were 40 records. In 2021, a photo of Clasping Milkweed taken in the Talladega Ranger District of the Talladega National Forest also contained three Edwards’ Hairstreaks, and an even larger colony was discovered.  Thirty-two individuals were recorded in one day. During late spring/early summer, small hairstreaks should be carefully examined to determine their identity--particularly near Alabama's eastern border where Edwards' occur.