I was standing on the verge beneath an oak tree when an insect dropped on to my bare arm. At first glance I thought it was a lacewing, but on closer inspection, something about it didn’t look quite right. A quick Google search revealed it was an oak snakefly (Phaeostigma notata), a bizarre insect you’ve probably never heard of. They are rarely encountered and under-recorded, not because they’re endangered, but because they’re arboreal and tend to stay hidden high in the canopy, or tucked away in bark cracks and crevices. But wind or heavy rain, like the gusty downpour we’d had that morning, can send them to lower levels.
It looked like a composite of insect body parts – a broad, flattened ant’s head, a housefly’s large compound eyes, spidery legs and damselfly-like wings with intricate venation. The presence of a formidable-looking long, needle‑like ovipositor indicated that this individual was female. Most unique was her elongated neck-like pronotum, which, when she reared up at the approach of my finger, gave her the appearance of a cobra poised to strike. It’s this distinctive feature that gives these fantastical creatures their colloquial name.
Snakeflies aren’t flies (Diptera). They’re related to the lacewings and antlions (Neuroptera), but are classified in a separate relictual order, Raphidioptera. They’re considered living fossils, as they closely resemble species from the early Jurassic period, about 140m years ago. There are about 260 extant snakefly species worldwide, all found in temperate regions of the northern hemisphere, but only four have been recorded in the UK.
Their strong mandibles seem at odds with a diet of soft-bodied prey, but they are voracious predators of aphids, mites and other small arthropods, their flexible pronotum enabling them to pursue prey into tight nooks and crannies. A recent stretch of warm weather, combined with high humidity, extended daylight hours and an abundance of succulent new growth, has created ideal conditions for an aphid population boom. Many trees in the locality have curled, distorted foliage – a telltale sign that sap-suckers have been piercing the leaf cuticle. But the oak was virtually unblemished, suggesting that the snakeflies are helping keep this damage in check.
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