Snakeflies are slender predatory insects in the order Raphidioptera, named for the way they raise their elongated “neck” in a posture that resembles a small snake poised to strike. With roughly 248 living species split between two families, they are among the least familiar insects you might encounter in a temperate forest, yet they belong to a lineage that stretches back hundreds of millions of years. Their story is one of ancient success followed by long, slow decline, and their biology is full of quirks that set them apart from the more familiar insects they superficially resemble.
What Makes a Snakefly Look Like a Snakefly
The most striking feature is the prothorax, the segment just behind the head, which is drawn out into a long cylinder. This gives the front of the body a neck-like profile that no other insect group really shares. The head itself is large, held roughly horizontal, and armed with strong biting mandibles. The antennae are long and threadlike, and the legs are all similar in shape, with the front pair attached at the very base of that elongated prothorax. Females carry a conspicuous needle-like ovipositor at the tip of the abdomen, which they use to insert eggs into bark crevices and similar tight spaces.1Oxford Academic. Observations on the Life History and Morphology of Agulla Bractea Carpenter (Neuroptera: Raphidiodea: Raphidiidae)
The wings are transparent and membranous, both pairs similar in size and shape, laced with a network of branching veins. They are neither particularly long nor particularly rounded, and a darkened patch called the pterostigma near the leading edge of each wing is easy to spot in most species. The wing venation includes a distinctive feature found nowhere else among their relatives: a particular fusion of two main veins near the wing base that takes on a shape unique to snakeflies.2American Museum Novitates. Wing Tracheation in Chrysopidae and Other Neuropterida (Insecta): A Resolution of the Confusion about Vein Fusion For the casual observer, the easiest identification cue is that long “neck” combined with four clear, veiny wings held roof-like over the body at rest. Nothing else in the insect world looks quite like it.
Where Snakeflies Live and Why You Rarely See Them
Snakeflies are almost exclusively creatures of the temperate Northern Hemisphere. They are most diverse in Europe, western Asia, and western North America, particularly in forested and mountainous regions. You will not find them in the tropics, the Southern Hemisphere, or anywhere that lacks sustained cold winters. This geographic restriction is not random. Snakefly larvae appear to need a prolonged chill period during development, and populations simply fail to establish where winters are mild or absent. That requirement effectively confines the entire order to a relatively narrow band of the planet’s surface.
Even within their range, snakeflies are easy to overlook. Adults are moderate-sized, typically around one to two centimeters in body length, and they spend most of their time in tree canopies or on bark, where their muted coloring blends in. They are day-active rather than drawn to lights at night, so they do not turn up at porch lamps the way many other insects do.3ScienceDirect. Encyclopedia of Insects Their adult lives are also relatively short, measured in weeks, so even in areas where they are common, the window to spot one is narrow.
Diet and Ecological Role
Both adults and larvae are predators. Adults of the family Raphidiidae, which contains the majority of living species, hunt during the day for soft-bodied arthropods: aphids, small caterpillars, mites, and similar prey. They also eat pollen, making them casual omnivores rather than strict carnivores. The diet of adults in the second living family, Inocelliidae, is much less understood. In captivity they accept artificial food, and pollen has only very rarely been found in their guts, so their natural feeding habits remain something of a mystery.4ScienceDirect. Encyclopedia of Insects
Larvae are more consistently predatory. They roam under bark or through soil, hunting other small invertebrates. Bark-dwelling larvae and soil-dwelling larvae tend to target different prey, so the group as a whole covers a fairly broad spectrum of small, soft-bodied food items. Because they eat pests like aphids and bark beetles, snakeflies are sometimes regarded as minor natural biocontrol agents in forests and orchards, though they are never abundant enough to make a dramatic dent in pest populations on their own.
Life Cycle and Development
Snakeflies undergo complete metamorphosis, passing through egg, larva, pupa, and adult stages. Females use that prominent ovipositor to deposit eggs in batches, tucking them into cracks in bark or similar sheltered spots. The larvae that emerge are elongated, somewhat flattened, and look vaguely like tiny, leggy centipedes. They are agile and actively predatory from birth.
The larval phase is the longest part of the life cycle and can stretch over one to several years depending on the species and conditions. During this time the larvae molt repeatedly, growing through multiple stages. As mentioned earlier, a period of sustained cold appears to be necessary to trigger pupation. Without a proper winter chill, larvae stall in development, which explains why snakeflies cannot colonize warm regions. The pupa is unusual for an insect that undergoes complete metamorphosis: it is not enclosed in a silk cocoon and remains mobile, capable of walking. This is a genuinely primitive trait, shared with a handful of other ancient insect lineages, and it means a snakefly pupa can reposition itself if disturbed, something a moth or butterfly pupa cannot do.
Courtship Rituals
Snakefly mating involves a structured courtship display that has been studied in several species of the genus Agulla in North America. The encounter unfolds in stages. Once a male and female are facing each other, the male begins a series of distinctive movements: vertical vibrations of the abdomen, lateral or vertical head motions, chewing movements of the mandibles, and gentle probing with the antennae. The female mirrors some of these behaviors at lower intensity but adds her own signature move, a slow, stretching, circular sweep of the abdomen.5Annals of the Entomological Society of America. Courtship and Mating Behavior in Agulla Species (Neuroptera: Raphidiidae)
The whole performance appears to function as a mutual assessment. If the female is unreceptive, she can simply walk away or become aggressive, and mating does not proceed. The face-to-face orientation is notable because it differs from the approach patterns seen in many other insect groups, where males approach from behind or from the side. In snakeflies, both partners seem to evaluate each other head-on before committing, which is a somewhat unusual dynamic for insects.
Two Living Families
All modern snakeflies belong to either Raphidiidae or Inocelliidae. Together they account for about 248 described species.6American Museum Novitates. Wing Tracheation in Chrysopidae and Other Neuropterida (Insecta): A Resolution of the Confusion about Vein Fusion Raphidiidae is the larger family, and its members are the ones most commonly encountered. Inocelliidae is smaller, with around seven living genera and roughly 44 species, distinguished from Raphidiidae partly by the absence of certain crossveins in the pterostigma region of the wing.7PubMed Central. Unraveling the evolutionary history of the snakefly family Inocelliidae (Insecta: Raphidioptera) through integrative phylogenetics
Within the broader insect family tree, Raphidioptera sits as a sister group to a combined clade of lacewings (Neuroptera) and alderflies/dobsonflies (Megaloptera).8PubMed Central. An integrative phylogenomic approach to elucidate the evolutionary history and divergence times of Neuropterida (Insecta: Holometabola) Together, these three orders make up the superorder Neuropterida. This grouping has been confirmed by large-scale genetic studies using modern sequencing techniques.9Systematic Entomology. Evolution of lacewings and allied orders using anchored phylogenomics (Neuroptera, Megaloptera, Raphidioptera) If you have ever seen a green lacewing fluttering around your garden, you have already met one of the snakefly’s closest relatives. The resemblance is there if you look: similar delicate wing venation, similar predatory habits, similar body plan minus the elongated “neck.”
DNA Barcoding and Hidden Species
As with many insect groups, the true number of snakefly species is almost certainly larger than the roughly 248 currently described. Modern DNA barcoding studies are helping to reveal the gaps. Work on Portuguese snakeflies, for example, found that genetic distances between recognized species were substantial, with some pairs of species differing by more than 15% in their barcode sequences, while variation within a single species was often less than 1-2%.10ZooKeys. DNA Barcoding of Portuguese Lacewings (Neuroptera) and Snakeflies (Raphidioptera) (Insecta, Neuropterida) Those clean gaps between species make DNA barcoding a powerful tool for flagging possible cryptic species, populations that look almost identical under a microscope but are genetically distinct enough to count as separate species.
Portugal alone has at least six known snakefly species, and the Iberian Peninsula more broadly is a hotspot for the group in Europe. Whether barcoding eventually pushes the global species count significantly higher remains to be seen. In many parts of Asia and the Middle East, snakefly diversity has barely been surveyed with molecular methods, so surprises are likely.
A Fossil Record of Former Glory
Snakeflies are ancient. Fossil evidence suggests that the diversification of major snakefly lineages was already well underway by the Early Jurassic period, roughly 200 million years ago, which implies the group had been evolving for a considerable time before that.11PubMed Central. New transitional fossil snakeflies from China illuminate the early evolution of Raphidioptera During the Mesozoic, snakeflies were far more diverse and widespread than they are today. Fossil forms have been found on every continent except Antarctica, including regions in the Southern Hemisphere where no snakeflies live now. Several entire families known only from fossils have no living descendants.
What is especially telling is how the group’s diversity has contracted over geological time. Snakefly larvae are well preserved in Cretaceous-age and Eocene-age amber, and comparisons between ancient and modern larvae reveal that the Cretaceous forms were more varied, particularly in head shape and antenna structure. That morphological variety was much greater than anything seen today.12PalZ. Declining morphological diversity in snakefly larvae during last 100 million years This physical shrinkage in variety mirrors the well-established loss of taxonomic diversity. It also likely signals a loss of ecological diversity: ancient snakeflies probably occupied a wider range of habitats and lifestyles than modern species do.
Within the surviving family Inocelliidae, the deepest splits between living genera trace back to the Eocene, roughly 40 to 50 million years ago, while most species-level diversification happened during the Miocene, roughly 5 to 23 million years ago.13PubMed Central. Unraveling the evolutionary history of the snakefly family Inocelliidae (Insecta: Raphidioptera) through integrative phylogenetics So while the order as a whole has been slowly losing ground since the Cretaceous, the species alive today are relatively recent arrivals within those surviving lineages.
Why Snakeflies Declined While Other Insects Thrived
The obvious question raised by the fossil record is: what happened? Why were snakeflies so much more diverse in the Cretaceous and so restricted today? The answer is not fully resolved, but the broad outlines are consistent across multiple studies. The end-Cretaceous mass extinction 66 million years ago wiped out many insect lineages, and snakeflies lost heavily. Several entire families disappeared. But the decline was not sudden. Diversity had already been narrowing before the asteroid impact, and the recovery afterward never came close to restoring former levels.
A major factor appears to be climate. The Cretaceous world was much warmer overall, and snakeflies evidently thrived in a wider range of thermal conditions than their modern descendants can tolerate. As global climates cooled and then fluctuated through ice ages, snakefly diversity contracted in step. The cold-winter requirement that restricts modern species to temperate zones may be a relatively recent evolutionary constraint, or at least a constraint that has tightened over time. The warm-climate lineages simply went extinct, and nothing replaced them. Meanwhile, the rise of flowering plants and the explosion of other insect orders, particularly beetles, flies, and wasps, reshaped terrestrial ecosystems in ways that may have squeezed snakeflies out of niches they formerly occupied.
Mistaken Identities and Common Mix-Ups
People who do notice a snakefly often mistake it for something else. The most common confusion is with lacewings, and understandably so. Green and brown lacewings share the same general wing structure: four transparent, vein-laced wings held tent-like over the body. But lacewings lack the elongated prothorax, so the silhouette is completely different in profile. Alderflies and dobsonflies, the other close relatives, are stockier and often much larger, and their wing venation has a different pattern.
Another common mix-up is with mantidflies (family Mantispidae), which are actually lacewings with raptorial forelegs that look startlingly like a praying mantis. Mantidflies can have an elongated front body section, so a quick glance might suggest a snakefly, but the grasping forelimbs are the giveaway. Snakefly legs are all similar in shape and none are modified for grabbing prey. If the front legs look like a mantis’s arms, it is a mantidfly, not a snakefly.
Some people also confuse snakeflies with certain parasitic wasps, especially the ichneumonids that carry long ovipositors. The ovipositor of a female snakefly can look superficially similar, but the wing venation and body proportions are very different. Wasps have a narrowed “waist” between thorax and abdomen; snakeflies do not.
Can You Attract or Keep Snakeflies
Snakeflies are not pests and pose no threat to humans. They do not bite people, sting, or damage property. If anything, they are mildly beneficial because they eat aphids and other small pests. There is no practical reason to control them, though there is also no easy way to attract them to your garden on purpose. Because they are tied to woodland habitats and tend to live in tree canopies, maintaining mature trees with rough bark is probably the single best thing you can do to encourage them. They lay eggs in bark crevices and their larvae develop under loose bark, so tidy, smooth-barked ornamental trees offer little habitat.
Keeping snakeflies in captivity is possible but uncommon. Entomologists who rear them report that the cold-winter requirement makes continuous culture in warm labs impractical. The larvae need months at low temperatures to complete development, and without that exposure they simply stall. This sensitivity to temperature is part of what makes snakeflies interesting to researchers studying how insects respond to climate change, but it also makes them finicky subjects for laboratory work.
Snakeflies and Climate Change
Given their narrow thermal requirements and their historical pattern of declining with warming climates, snakeflies are a group that researchers watch with some concern as global temperatures rise. Their fossil record already demonstrates what happens when warm conditions expand and cold conditions shrink: snakefly diversity drops. If modern warming eliminates the sustained winter cold that larvae need, populations at the warm edges of their range could fail to reproduce.
At the same time, warming could open new habitat at higher latitudes and elevations, so the picture is not necessarily one of pure loss. Mountain populations may shift upslope, and boreal forests may see colonization by species currently limited to more southerly latitudes. Whether the gains can keep pace with the losses is unknown. The fact that snakeflies have never recovered the diversity they lost during past warm periods is not especially encouraging, but past warmings also did not have the kind of rapid, human-assisted habitat change that characterizes the current era. The interaction between temperature shifts and habitat fragmentation could make things harder for a group that was already in long-term decline well before humans arrived.