thumb|left|Resting female in [[Rio Grande Valley (Texas)|Rio Grande Valley, Texas, USA]]
The great purple hairstreak (Atlides halesus), also called the great blue hairstreak, is a common gossamer-winged butterfly species in parts of the United States. It is actually a Neotropical species; its North American range only includes the warm-temperate and subtropical parts of that continent, and it ranges southwards almost to the Isthmus of Panama. The type specimen, however, was shipped to Europe from the Colony of Virginia, probably around the time of the United States Declaration of Independence.
The common names refer to the butterfly's two main colors – dusky purple on the underside, and iridescent blue above. Particularly the males are very colorful in flight – brilliant blue and velvety black, with bright red and golden markings – but when sitting down they show their inconspicuous dusky purple underside. On each hindwing, there are two tails, with one short and one long tail, lending itself to the name "hairstreak". The abdomen of the butterfly features a blue upper-side and an orange under-side.
Like other butterfly species, the morphology of Atlides halesus hindwings mimic a head. The combination of the tails, resembling antennae of a butterfly, along with the orange spots on each hind-wing, which resembles eyes, gives the butterfly a "false head". When perching, the butterfly will also orient their body so the tails point upwards while the real head points downwards, in addition to moving their bodies back and forth. The eggs appear white with a hard and solid outer surface. During oviposition, female butterflies will lay as many as twenty single eggs at different locations on the leaves of a mistletoe plant.
Larvae
After hatching, larvae will emerge from the top of the egg, leaving behind an opening at the top of the egg. Instead, they go straight into feeding on their host plant's leaves and male flowers until fully grown. The species gains protective toxins from their larval host plants that stay in their system into adulthood. Caterpillars will feed on the leaves of their host plant until time of pupation, which is around 20 days from hatching to pupation.