Snakeflies are a group of insects in the order Raphidioptera, consisting of about 150 species. Together with the Megaloptera they were formerly placed within the Neuroptera, but now these two are generally regarded as separate orders.
Raphidioptera are characterized by having an elongate prothorax but no modification of the forelegs (as in Mantispidae). They possess ocelli and females typically have a long ovipositor. Snakeflies are predatory, both as adults and larvae. They can be quite common throughout temperate Europe and Asia, but in North America occur exclusively in the Western United States, namely in the Rocky Mountains as their larvae require cool temperatures to develop.
The two extant families of snakeflies are the Raphidiidae and Inocelliidae. In addition, there are a number of extinct forms known only from fossils. Almost all known snakeflies belong to the suborder Raphidiomorpha. The single exception is the prehistoric family Priscaenigmatidae, sometimes placed in a suborder Priscaenigmatomorpha but more likely a basal lineage that does not warrant the establishment of such a redundant monotypic taxon.
Fossil snakeflies are known from the Early Cretaceous onwards and these are not even the basalmost forms, suggesting their origin lies deep in the Jurassic at least. In fact, the earliest Neuroptera are from the Permian and thus snakefly ancestors probably even predate the Mesozoic also. Fossil Raphidiomorpha taxa are: