Snake Fly

Order Raphidioptera — the snake flies — is one of the smallest insect orders in terms of species diversity (~250 species worldwide) and one of the most ancient surviving holometabolous lineages (with confirmed fossils dating to the Permian, ~270 million years ago). The order's defining anatomical feature is the dramatically elongated, flexible prothorax (the segment of the thorax between the head and the wing-bearing segments) — it can be 2-3x the length of the head and is held vertically when the insect is alert, allowing the head to rear up cobra-like over the body. The 'snake' analogy is the basis of every common name in every language for the order. Adult snake flies are 8-15 mm long with two pairs of clear veined wings, large compound eyes, and chewing mouthparts. They are predators of small soft-bodied insects (aphids, scale insects, mealybugs, small caterpillars, mite eggs), particularly on tree bark and conifer needles. Larvae are similarly predatory — long flexible elongated grubs that hunt under bark and in soil. The order's most-cited biogeographic mystery is its STRICT Northern Hemisphere distribution. Despite extensive entomological survey across the Southern Hemisphere over 200+ years, no snake fly has EVER been documented south of the equator. The disjunction is anomalous given the order's ancient origins (Pangaea was unified at the Permian origin of the lineage, so an even Northern/Southern distribution would be expected). The current consensus is that snake flies originated in the Permian Northern Hemisphere supercontinent Laurasia, never colonized the Gondwanan southern landmass, and have remained restricted to the Northern Hemisphere ever since — making the order one of the most paleobiogeographically interesting insects on Earth. R. notata is a common European species widespread across the continent.