Snakefly

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Snakefly
Temporal range: Lower Jurassic–Recent
Raphidia notata beentree.jpg
Female Dichrostigma flavipes
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Clade: Neuropterida
Order: Raphidioptera
Handlirsch, 1908
Suborders

Raphidiomorpha
Priscaenigmatomorpha

Synonyms
  • Raphidiodea

Snakeflies are a group of predatory insects 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 temperate regions worldwide but are absent from the tropics and the Southern Hemisphere. Recognisable 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.

Contents

An adult snakefly resembles a lacewing 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, larvae, pupae 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 arthropods.

Description

Wings of Raphidia ophiopsis showing coloured pterostigmata Raphidia ophiopsis M NL-Doorwerth-19540617 right wing - collection Naturalis.jpg
Wings of Raphidia ophiopsis showing coloured pterostigmata

Adult snakeflies are easily distinguished from similar insects by having an elongated prothorax but not the modified forelegs of the mantis-flies. Most species are between 15 and 30 mm (0.6 and 1.2 in) in length. The head is long and flattened, and heavily sclerotised; it may be broad or taper at the back, but is very mobile. The mouthparts are strong and relatively unspecialised, being modified for biting. The large compound eyes are at the sides of the head. Members of the family Inocelliidae have no simple eyes; members of the Raphidiidae do have such eyes, but are mostly differentiated by elimination, lacking the traits found in inocelliids. The prothorax is notably elongated and mobile, giving the group its common name of snakefly. The three pairs of legs are similar in size and appearance. The two pair of dragonfly-like wings are similar in size, with a primitive venation pattern, a thickened leading edge, and a coloured wingspot, the pterostigma. Inocelliids lack a cross vein in the pterostigma that is present in raphidiids. The females in both families typically have a long ovipositor, which they use to deposit their eggs into crevices or under bark. [1] [2] [3] [4]

Distribution and habitat

Snakeflies are usually found in temperate coniferous forest. They are distributed widely around the globe, the majority of species occurring in Europe and Asia, but also being found in certain regions of Africa, western North America and Central America. In Africa, they are only found in the mountains north of the Sahara Desert. In North America, they are found west of the Rocky Mountains, and range from southwest Canada all the way to the Mexican-Guatemalan Border, which is the furthest south they have been found in the western hemisphere. In the eastern hemisphere, they can be found from Spain to Japan. Many species are found throughout Europe and Asia with the southern edge of their range in northern Thailand and northern India. [5] Snakeflies have a relict distribution, having had a more widespread range and being more diverse in the past; there are more species in Central Asia than anywhere else. [3] In the southern parts of their range, they are largely restricted to higher altitudes, up to around 3,000 m (10,000 ft). [4] Even though this insect order is widely distributed, the range of individual species is often very limited and some species are confined to a single mountain range. [6]

Life cycle

Larva Rhaphidioptera-larva.jpg
Larva

Snakeflies are holometabolous insects, having a four-stage life cycle with eggs, larvae, pupae and adults. Before mating, the adults engage in an elaborate courtship ritual, including a grooming behaviour involving legs and antennae. In raphidiids, mating takes place in a "dragging position", while in inocelliids, the male adopts a tandem position under the female; copulation may last for up to three hours in some inoceliid species. The eggs are oviposited into suitable locations and hatch in from a few days to about three weeks. [4]

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 prolegs. However, they do possess an adhesive organ on the abdomen, which they can use to fasten themselves to vertical surfaces. [1]

There is no set number of instars 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. [5] The final larval instar, the prepupal stage, creates a cell in which the insect pupates. 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. [7] All snakeflies require a period of cool temperatures (probably around 0 °C (32 °F)) to induce pupation. [5] 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. [5] 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. [4]

Ecology

Adult snakeflies are territorial and carnivorous organisms. They are diurnal and are important predators of aphids and mites. 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. [5] [4] 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, springtails, spiders, barklice, sternorrhynchids and auchenorrhynchids. [3] The actual diets of the larvae vary according to their habitats, but both larvae and adults are efficient predators. [4]

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. [8] Typically 5-15% of snakefly larvae are parasitized, mainly by parasitoid wasps, but rates as high as 50% have been observed in some species. [5]

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. [4] They have been considered living fossils, because modern-day species closely resemble species from the early Jurassic period (140 mya). [6] There are about 260 extant species. [5]

Fossil history

Several extinct families are known only from fossils dating from the Lower Jurassic to the Miocene, [9] the great majority of them belonging to the suborder Raphidiomorpha. [9] The transitional Middle Jurassic Juroraphidiidae form a clade with the Raphidiomorpha. [10]

Phylogeny

Molecular analysis using mitochondrial RNA and the mitogenome has clarified the group's phylogeny within the Neuropterida, as shown in the cladogram. [11] [12]

Neuropterida

Raphidioptera (snakeflies) Snakefly R. confinis%3F (cropped).jpg

Megaloptera (alderflies and allies) Schlammfliege Sialis sp 5325.jpg

Neuroptera

Osmylidae (giant lacewings) Oedosmylus sp crop.jpg

Hemerobiiformia (lacewings) Micromus variegatus01.jpg

Myrmeleontiformia (antlions and allies) Distoleon tetragrammicus01.jpg

The name Raphidioptera is formed from Greek ῥαφίς (raphis), meaning needle, and πτερόν (pteron), meaning wing. [13]

The Megaloptera, Neuroptera (in the modern sense) and Raphidioptera are very closely related, forming the group Neuropterida. [14] 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 beetles. [15]

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. [9] [16] [17] Raphidioptera

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. [6] 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. [4]

Related Research Articles

<span class="mw-page-title-main">Neuroptera</span> Order of insects

The insect order Neuroptera, or net-winged insects, includes the lacewings, mantisflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera is grouped together with the Megaloptera and Raphidioptera (snakeflies) in the unranked taxon Neuropterida.

<span class="mw-page-title-main">Megaloptera</span> Order of insects

Megaloptera is an order of insects. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known species.

<span class="mw-page-title-main">Mantispidae</span> Family of insects

Mantispidae, known commonly as mantidflies, mantispids, mantid lacewings, mantisflies or mantis-flies, is a family of small to moderate-sized insects in the order Neuroptera. There are many genera with around 400 species worldwide, especially in the tropics and subtropics. Only five species of Mantispa occur in Europe. As their names suggest, members of the group possess raptorial forelimbs similar to those of the praying mantis, a case of convergent evolution.

<span class="mw-page-title-main">Osmylidae</span> Family of insects

Osmylidae are a small family of winged insects of the net-winged insect order Neuroptera. The osmylids, also called lance lacewings, stream lacewings or giant lacewings, are found all over the world except North and Central America. There are around 225 extant species.

<span class="mw-page-title-main">Hemerobiidae</span> Family of insects

Hemerobiidae is a family of Neuropteran insects commonly known as brown lacewings, comprising about 500 species in 28 genera. Most are yellow to dark brown, but some species are green. They are small; most have forewings 4–10 mm long. These insects differ from the somewhat similar Chrysopidae not only by the usual coloring but also by the wing venation: hemerobiids differ from chrysopids in having numerous long veins and forked costal cross veins. Some genera are widespread, but most are restricted to a single biogeographical realm. Some species have reduced wings to the degree that they are flightless. Imagines (adults) of subfamily Drepanepteryginae mimic dead leaves. Hemerobiid larvae are usually less hairy than chrysopid larvae.

<span class="mw-page-title-main">Neuropterida</span> Clade of insects

The Neuropterida are a clade, sometimes placed at superorder level, of holometabolous insects with over 5,700 described species, containing the orders Neuroptera, Megaloptera, and Raphidioptera (snakeflies).

<span class="mw-page-title-main">Berothidae</span> Family of insects

The Berothidae are a family of winged insects of the order Neuroptera. They are known commonly as the beaded lacewings. The family was first named by Anton Handlirsch in 1906. The family consists of 24 genera and 110 living species distributed discontinuously worldwide, mostly in tropical and subtropical regions. Numerous extinct species have also been described. Their ecology is poorly known, but in the species where larval stages have been documented, the larvae are predators of termites.

<span class="mw-page-title-main">Nevrorthidae</span> Family of insects

The Nevrorthidae are a small family of lacewings in the order Neuroptera. There are 19 extant species in four genera, with a geographically disjunct distribution: Nevrorthus, comprising 5 species with scattered distributions around the Mediterranean; Austroneurorthus, with two species known from southeastern Australia; Nipponeurorthus, comprising 11 species known from China and Japan; and Sinoneurorthus, known from a single species described from Yunnan Province, China. They are traditionally placed in the Osmyloidea, alongside Osmylidae and the spongillaflies (Sisyridae), but some research has considered them to be the sister group to the rest of Neuroptera. The larvae have unique straight jaws that are curved at the tips, and live as unspecialised predators in the sandy bottom sediments of clear, fast flowing mountain rivers and streams. They pupate underwater on the underside of stones. The adults are likely predators or feed on honeydew and other sugar-rich fluids.

<span class="mw-page-title-main">Nymphidae</span> Family of insects

Nymphidae, sometimes called split-footed lacewings, are a family of winged insects of the order Neuroptera. There are 35 extant species native to Australia and New Guinea.

<span class="mw-page-title-main">Psychopsidae</span> Family of insects

Psychopsidae is a family of winged insects of the order Neuroptera. They are commonly called silky lacewings.

<span class="mw-page-title-main">Sisyridae</span> Family of insects

Sisyridae, commonly known as spongeflies or spongillaflies, are a family of winged insects in the order Neuroptera. There are approximately 60 living species described, and several extinct species identified from the fossil record.

<span class="mw-page-title-main">Coniopterygidae</span> Family of insects

The dustywings, Coniopterygidae, are a family of Pterygota of the net-winged insect order (Neuroptera). About 460 living species are known. These tiny insects can usually be determined to genus with a hand lens according to their wing venation, but to distinguish species, examination of the genitals by microscope is usually necessary.

<i>Styporaphidia</i> Extinct genus of insects

Styporaphidia is a genus of snakefly, belonging to the extinct family Mesoraphidiidae, containing up to three species, the type species Styporaphidia magia, Styporaphidia willmanni and tentatively Styporaphidia? hispanica. The genus was named from the Greek stypos meaning "stem" or "stump" and Raphidia, the type genus for, and most often used as, a stem for generic names in the order Raphidioptera. The species name of S. magia is from the Greek word mageia meaning "magic" while the species name for S.? hispanica is from the Latin Hispania meaning "Spain" in reference to the type locality of the species.

<span class="mw-page-title-main">Ithonidae</span> Family of insects

Ithonidae, commonly called moth lacewings and giant lacewings, is a small family of winged insects of the insect order Neuroptera. The family contains a total of ten living genera, and over a dozen extinct genera described from fossils. The modern Ithonids have a notably disjunct distribution, while the extinct genera had a more global range. The family is considered one of the most primitive living neuropteran families. The family has been expanded twice, first to include the genus Rapisma, formerly placed in the monotypic family Rapismatidae, and then in 2010 to include the genera that had been placed into the family Polystoechotidae. Both Rapismatidae and Polystoechotidae have been shown to nest into Ithonidae sensu lato. The larvae of ithonids are grub-like, subterranean and likely phytophagous.

<i>Necroraphidia</i> Extinct genus of insects

Necroraphidia is an extinct genus of snakefly in the family Mesoraphidiidae. The genus is solely known from Early Cretaceous, Albian age, fossil amber found in Spain. Currently the genus comprises a single species, Necroraphidia arcuata.

<i>Amarantoraphidia</i> Extinct genus of insects

Amarantoraphidia is an extinct genus of snakefly in the family Mesoraphidiidae. The genus is solely known from Early Cretaceous, Albian age, fossil amber found in Spain. Currently the genus comprises only a single species Amarantoraphidia ventolina.

<i>Cantabroraphidia</i> Extinct genus of insects

Cantabroraphidia is an extinct genus of snakefly in the family Mesoraphidiidae. The genus is solely known from fossil amber found in Cantabria, northern Spain, dating to the Albian age of the Early Cretaceous Period. Currently the genus comprises a single species Cantabroraphidia marcanoi.

<span class="mw-page-title-main">Mesoraphidiidae</span> Extinct family of insects

Mesoraphidiidae is an extinct family of snakeflies in the suborder Raphidiomorpha. The family lived from the Late Jurassic through the Late Cretaceous and is known from twenty-five genera. Mesoraphidiids have been found as both compression fossils and as inclusions in amber. The family was first proposed in 1925 by the Russian paleoentomologist Andrey Vasilyevich Martynov based on Upper Jurassic fossils recovered in Kazakhstan. The family was expanded in 2002 by the synonymizing of several other proposed snakefly families. The family was divided into three subfamilies and one tribe in a 2011 paper, further clarifying the relationships of the included genera.

Iberoraphidia is an extinct genus of snakefly in the family Mesoraphidiidae. The genus is solely known from a Cretaceous, Lower Barremian, fossil found in Spain. Currently the genus is composed of a single species, Iberoraphidia dividua.

This list of fossil arthropods described in 2011 is a list of new taxa of trilobites, fossil insects, crustaceans, arachnids and other fossil arthropods of every kind that have been described during the year 2011. The list only includes taxa at the level of genus or species.

References

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Further reading