Invertebrates
Gray Hairstreak
Strymon melinus · also called gray hairstreaks
Perched on a flower head, a gray hairstreak slowly rubs its hindwings together, making a pair of thread-like false antennae wiggle at the rear of its wings, a small deception aimed entirely at convincing an approaching predator to attack the wrong end of the butterfly.
Overview
The gray hairstreak, Strymon melinus, is a small, fast-flying butterfly native to grassland and other open habitat across a very broad range spanning most of North, Central, and South America. Its convincing false-head wing decoy, unusually wide range of caterpillar host plants, and status as one of the most widespread butterflies in the Americas make it one of the more behaviourally clever and ecologically adaptable butterflies found across the continent.
A butterfly with two ends and one decoy
Few insects rely on a false head as convincingly as the gray hairstreak, whose combination of a fake-antennae wing pattern and a deliberate wing-rubbing motion turns a simple wing marking into an active, moving decoy.
Status
Least Concern — extremely widespread and common across suitable grassland and open habitat throughout most of the Americas.
Gray Hairstreak: common questions
Why does the gray hairstreak have a fake head on its wings?
This species displays a false head pattern at the rear of its hindwings, complete with thin, thread-like tails resembling antennae, a decoy that encourages predators such as birds to attack the wrong end of the butterfly, giving the real head and body a better chance of escaping relatively unharmed from an attack that only damages a less vital part of the wing.
How does the gray hairstreak make its fake antennae move?
This species frequently rubs its hindwings together while perched, a subtle motion that makes the thread-like false antennae at the rear of the wings wiggle back and forth, closely mimicking the movement of a real insect's antennae and further reinforcing the illusion of a head where there isn't one.
Why is the gray hairstreak found almost everywhere?
This species feeds on an unusually wide variety of host plants as a caterpillar, including many different legumes, mallows, and other common plants, a dietary flexibility that has allowed it to establish itself across an extremely broad range spanning most of North, Central, and South America.
Can the gray hairstreak damage garden crops?
Its caterpillar frequently feeds on the flowers and developing seed pods of host plants rather than only leaves, and because beans, peas, and other legumes are among its many acceptable host plants, it can occasionally cause minor damage to these crops in gardens, though it is not generally considered a major agricultural pest.