Hairstreaks

Definition

A common name for butterflies of the subfamily Theclinae (family Lycaenidae, the gossamer-winged butterflies), characterized by small to medium size and, in most species, thin tail-like extensions on the hindwings with adjacent eyespot markings. These 'tails' and eyespots function in predator deflection, diverting attacks away from the head and body. The group includes diverse tropical species, often with structural blue iridescence on the upper wing surface, and temperate North American forms typically brown above. Some members are alternatively called elfins.

Etymology

From the hair-like tail extensions on the hindwings of typical species.

Example

The gray hairstreak (Strymon melinus) is one of the most widespread hairstreaks in North America, recognized by its gray-brown upper wings and the thin, hair-like tail with orange-capped eyespot on each hindwing.

Synonyms

• theclines

Related Terms

• Lycaenidae
• Gossamer-winged butterflies
• elfins
• deflection marking
• predator deflection
• structural coloration
• Theclinae

Usage Notes

Used as a plural common name for the subfamily; individual species are 'a hairstreak.' Not all Theclinae possess the eponymous tails—some tropical species and the 'elfins' (small, tailless members) lack this feature. The term 'thecline' (adjective/noun) is the technical equivalent but rarely used outside taxonomic literature. Hairstreaks are distinguished from other lycaenid subfamilies (blues, coppers, hairstreaks) by hindwing morphology and larval host-plant associations, often with oaks, legumes, or mistletoes.