Product Code Database
Snakeflies are a group of predatory comprising the order Raphidioptera with two extant families: Raphidiidae and Inocelliidae, consisting of roughly 260 species. In the past, the group had a much wider distribution than it does now; snakeflies are found in worldwide but are absent from the tropics and the Southern Hemisphere. Recognizable representatives of the group first appeared during the Early Jurassic. They are a relict group, having reached their apex of diversity during the Cretaceous before undergoing substantial decline.
An adult snakefly resembles a Hemerobiiformia in appearance but has a notably elongated thorax which, together with the mobile head, gives the group their common name. The body is long and slender and the two pairs of long, membranous wings are prominently veined. Females have a large and sturdy ovipositor which is used to deposit eggs in some concealed location. They are holometabolous insects with a four-stage life cycle consisting of eggs, , and adults. In most species, the larvae develop under the bark of trees. They may take several years before they undergo metamorphosis, requiring a period of chilling before pupation takes place. Both adults and larvae are predators of soft-bodied .
The larvae have large heads with projecting mandibles. The head and the first segment of the thorax are sclerotised, but the rest of the body is soft and fleshy. They have three pairs of true legs, but no . However, they do possess an adhesive organ on the abdomen, which they can use to fasten themselves to vertical surfaces.
There is no set number of the larvae will go through, some species can have as many as ten or eleven. The larval stage usually lasts for two to three years, but in some species can extend for six years. The final larval instar, the prepupal stage, creates a cell in which the insect . The pupa is able to bite when disturbed, and shortly before the adult emerges, it gains the ability to walk and often leaves its cell for another location. Kovarik, P. et al. (1991) Development and behavior of a snakefly, Raphidia bicolor Albada (Neuroptera: Raphidiidae) All snakeflies require a period of cool temperatures (probably around ) to induce pupation. The length of the pupation stage is variable. Most species pupate in the spring or early summer, and take a few days to three weeks before ecdysis. If the larvae begin pupation in the late summer or early fall, they can take up to ten months before the adults emerge. Insects reared at constant temperatures in a laboratory may become "prothetelous", developing the compound eyes and wingpads of pupae, but living for years without completing metamorphosis.
Predators of snakeflies include birds; in Europe, these are woodland species such as the treecreeper, great spotted woodpecker, wood warbler, nuthatch, and dunnock, as well as generalist insect-eating species such as the collared flycatcher. Typically 5-15% of snakefly larvae are parasitized, mainly by , but rates as high as 50% have been observed in some species.
File:ZooKeys-204-001-g007 Amarantoraphidia 01.jpg| Amarantoraphidia (†Mesoraphidiidae) in Early Cretaceous amber, Spain
File:Ohmella coffini holotype (cropped).jpg| Ohmella coffini (Raphidiidae) from the Miocene of France
The name Raphidioptera is formed from Greek ῥαφίς ( raphis), meaning needle, and πτερόν ( pteron), meaning wing.
The Megaloptera, Neuroptera (in the modern sense) and Raphidioptera are very closely related, forming the group Neuropterida.
Two suborders of Raphidioptera and their families are grouped below according to Engel (2002) with updates according to Bechly and Wolf-Schwenninger (2011) and Ricardo Pérez-de la Fuente et al. (2012). For lists of genera, see the articles on the individual families.
Raphidioptera
Ecology
Adult snakeflies are territorial and carnivorous organisms. They are diurnal and are important predators of and . Pollen has also been found in the guts of these organisms and it is unclear whether they require pollen for part of their lifecycle or if it is a favoured food source. The larvae of many raphidiids live immediately below the bark of trees, although others live around the tree bole, in crevices in rocks, among leaf litter and in detritus. Here they feed on the eggs and larvae of other arthropods such as mites, , , barklice, Sternorrhyncha and Auchenorrhyncha. The actual diets of the larvae vary according to their habitats, but both larvae and adults are efficient predators.
Evolution
During the Mesozoic era (252 to 66 mya), there was a large and diverse fauna of Raphidioptera as exemplified by the abundant fossils that have been found in all parts of the world. This came to an abrupt end at the end of the Cretaceous period, likely as a result of the Cretaceous–Paleogene extinction event (66 mya) when an enormous asteroid is thought to have hit the Earth. This seems to have extinguished all but the most cold-tolerant species of snakefly, resulting in the extinction of the majority of families, including all the tropical and sub-tropical species. The two families of present-day Raphidioptera are thus relict populations of this previously widespread group. They have been considered , because modern-day species closely resemble species from the early Jurassic period (140 mya). There are about 260 Extant taxon species.
Fossil history
Several extinct families are known only from dating from the Lower Jurassic to the Miocene, the great majority of them belonging to the suborder Raphidiomorpha. The transitional Middle Jurassic Juroraphidiidae form a clade with the Raphidiomorpha.
Phylogeny
Molecular analysis using RNA and the mitogenome has clarified the group's phylogeny within the Neuropterida, as shown in the cladogram.
(2025). 9781118945582, John Wiley & Sons Ltd.. ISBN 9781118945582 This is either placed at superorder rank, with the Holometabola – of which they are part – becoming an unranked clade above it, or the Holometabola are maintained as a superorder, with an unranked Neuropterida being a part of them. Within the holometabolans, the closest living relatives of Neuropterida are the .
Possible biological pest control agents
Snakeflies have been considered a viable option for biological control of agricultural pests. The main advantage is that they have few predators, and both adults and larvae are predacious. A disadvantage is that snakeflies have a long larval period, so their numbers increase only slowly, and it could take a long time to rid crops of pests; another issue is that they prey on a limited range of pest species. An unidentified North American species was introduced into Australia and New Zealand in the early twentieth century for this purpose, but failed to become established.
Further reading
External links
|
|
