AT A GLANCE
- Common Name: Hornet Moth
- Scientific Name: Sesia apiformis
- Category: Invertebrates
- Subcategory: Insects
- Range: Widespread across Europe and western Asia, from the British Isles and southern Scandinavia south to the Mediterranean and east to the Urals; introduced to North America
- Habitat Type: Lowland wetlands, riverbanks, parklands, fens, and roadsides where mature black poplars, hybrid poplars, trembling aspens, and willows grow
- IUCN Red List Status: Not Evaluated (locally common and secure)
- Lifespan: Adult lives 7 to 14 days; larval stage lasts 2 to 3 years inside tree trunks
- Diet: Herbivorous (adults have non-functional mouthparts and do not feed; larvae feed on the bark, cambium, and solid wood of poplar and willow roots and lower trunks)
- Average Size/Weight: Wingspan 35 to 48 mm; body length 20 to 28 mm (one of Europe’s largest clearwing moths)
- Key Defining Feature: Flawless Batesian mimic of the European Hornet, featuring transparent clear wings, a thick black abdomen boldly striped in bright yellow, and a yellow-and-black head that completely fools predators
Overview
The Hornet Moth (Sesia apiformis), also known as the Hornet Clearwing, is one of the most astounding and convincing examples of Batesian mimicry in the insect kingdom. Belonging to the clearwing moth family Sesiidae, this harmless, day-flying moth possesses no sting, no venom, and no mouthparts—yet it looks, sounds, and behaves so completely like a fearsome European Hornet (Vespa crabro) that birds, predators, and even experienced human observers recoil in fear.
Biology and Physical Characteristics
Sesia apiformis is a large, stout-bodied moth with a wingspan of up to 48 mm. Unlike typical moths whose wings are covered in opaque, powdery scales, its wings are mostly transparent and glass-like (clearwing), bordered only by narrow margins of rusty-brown scales. Its robust abdomen is cylindrical, heavily built, and vividly ringed with alternating bands of glossy jet-black and bright lemon-yellow, ending in a blunt tip that mimics a hornet’s sting. The thorax is dark brown with two prominent, circular yellow patches on the shoulders, and the head is bright yellow. Even its legs are thick, orange-yellow, and hairy, perfectly matching the limb anatomy of a large social wasp.
Behavior and Ecology
Adult Hornet Moths emerge from late May through July. When emerging from their pupal cases at the base of mature poplar trees, they crawl onto the bark in early morning sunlight to dry their wings. When resting or walking, the moth mimics the jerky, deliberate movements of a hornet, and when alarmed, it curves its abdomen downward in a convincing mock-stinging display. The female deposits eggs in bark crevices around the base of black poplars (Populus nigra) and aspens. The hatching caterpillars bore deep into the tree’s wood and root crown, spending two to three years tunneling through solid timber before pupating just beneath the outer bark.
Conservation and Human Impact
The Hornet Moth has not been evaluated by the IUCN, but is widely distributed throughout temperate Europe. Because its larvae develop inside mature poplars and willows, it is dependent on the retention of mature trees in parks, river corridors, and rural hedgerows. The widespread felling of old black poplars has led to localized declines in parts of Western Europe, but it remains secure overall.
Interesting Factoid
The Hornet Moth is completely harmless with no sting and no mouth, but it mimics the terrifying European Hornet so perfectly—down to its yellow stripes, clear wings, and jerky walk—that almost no bird dares to touch it.