Raphidioptera

(Snakeflies)

Class Insecta

Order Raphidioptera

Number of families 2

Evolution and systematics

An enormous abundance and diversity of raphidiopteran fossils occur in Jurassic and Cretaceous deposits, within the Mesozoic era. The extraterrestrial impact that occurred 65 million years ago probably led to the extinction of most snake-flies. Raphidioptera from the Tertiary belong to the two extant (non-extinct) families. They represent living fossils. Raphidioptera are currently considered the sister group of Megaloptera and Neuroptera, and all three orders constitute the superorder Neuropterida at the base of the Holometabola— the group of orders containing species that undergo complete metamorphosis. The order Raphidioptera comprises two homogeneous families: Raphidiidae, with 185 species, and Inocelliidae, with 21 described species. The estimated number of extant species may be around 250.

Physical characteristics

Raphidioptera have narrow bodies with an elongate pronotum, movable head, and two pairs of subequal wings whose forewings range from 0.20 to 0.79 in (5 to 20 mm). The head is prognathous, flattened dorsoventrally, with chewing mouthparts, large compound eyes, and in the Raphidiidae, with three dorsal ocelli. The wing venation is net-like, and the hyaline wing membrane contrasts with a bright yellow, brown, or bicolored pterostigma. Females have a long ovipositor, and male genitals may be spectacularly shaped. Larvae are terrestrial and elongate, with a flat prognathous head, chewing mouthparts, and 4 to 7 stemmata. The head and prothorax are strongly sclerotized (hardened), while the mesoand metathorax and abdomen are soft-bodied. Preimaginal pupae are extremely mobile and, except for their small wing pads, are similar to adults.

Distribution

Extant Raphidioptera occur throughout the Holarctic region but have not been found in the northern and eastern parts of North America. Their distribution comprises almost all arboreal parts of the Palaearctic region, including fringes of the Oriental region, with the southernmost records (at higher altitudes) in Morocco, northern Algeria, northern Tunisia, Israel, Syria, northern Iraq, northern Iran, northern Pakistan, northern India, Bhutan, Myanmar, northern Thailand, and Taiwan. In the Nearctic region their distribution is restricted to the southwestern and southern parts of North America; the southernmost records are from the Mexican-Guatemalan border. Most species have small distribution areas and are often restricted to a single mountain range.

Habitat

Snakeflies are restricted to bushy arboreal woodland habitats and to latitudes and/or altitudes with a pronounced winter period, and from sea level to more than 9,840 ft (3,000m). Larvae live under the bark of trees or shrubs (many Raphidiidae, all Inocelliidae) or in the top layer of soil (Raphidiidae). Larvae of a few species sometimes also live in rock crevices.

Behavior

Snakeflies are solitary. Premating communication via antennae and movements of abdomen and wings has been observed in several species. Adults are active only during daytime, where they spend much of their time grooming themselves, combing their foretibiae against parts of the ventrally bent head and then pulling their antennae between their tibiae. As they retract their legs, the tibiae and tarsi are pulled through the mouthparts. Cleaning of the mouthparts starts with moving one mandible aside and proceeds with moving the palps and all other parts against each other. Snakeflies are poor flyers with an extremely low vagility and thus have little capacity for dispersal.

Feeding ecology and diet

Larvae of all snakeflies and adults of Raphidiidae are predaceous, feeding on softskinned arthropods. Adults of both families have been observed feeding on pollen.

Reproductive biology

Two positions of copulation have been found: a "wrecking position" (in Raphidiidae), in which the male hangs head first from the female, being carried by her; and a "tandem position" (in Inocelliidae), in which the male crawls under the female, attaching his head in fixed connection to the fifth abdominal sternite of the female. Copulation lasts a few minutes to 1.5 hours in Raphidiidae and up to three hours in Inocelliidae. Oval cigarlike eggs are laid singly or in a batch by the long ovipositor into crevices of bark or under litter. The egg stage lasts from a few days up to three weeks. The larval period lasts at least one year and at most two or three years, although under experimental conditions the period can stretch up to six years. The number of larval instars is generally 10 or 11 but may reach 15 or more. Pupation occurs in spring, and the pupal stage lasts from a few days up to three weeks. In some species pupation takes place in summer or autumn, and the pupal stage lasts several months, up to 10. The extreme mobility of the pupa is a remarkable primitive feature of snakeflies.

Hibernation may occur in the last larval stage, the penultimate larval stage, or the pupa stage, but never in the egg, prepupa, or adult stages. Snakeflies require a low-temperature period (around 32°F [0°C]) to induce pupation or hatching of the imago. Larvae are often parasitized by various species of the families Ichneumonidae (in particular of the genus Nemeritis) and Braconidae.

Conservation status

Almost all species are restricted to limited areas of refugial character, and a high number of species are endemic to certain mountain ranges or islands. Only three species occur throughout northern Asia to northern and central Europe, while a few species in North America, with distribution centers in the Southwest, have succeeded in reaching southern Canada. Although no species are listed by the IUCN, several species with small distributions are seriously endangered by habitat destruction.

Significance to humans

Woodcut illustrations of snakeflies appeared in the seventeenth century, and first species descriptions were published in the eighteenth century. Several species are beneficial to humans as predators of aphids and other soft-bodied pest arthropods, but trials to introduce them into Australia for biological control failed.

Species accounts

List of Species

Schummel's inocelliid snakefly

Inocellia crassicornis

family

Inocelliidae

taxonomy

Raphidia crassicornis Schummel, 1832, near Scheitnich (Silesia), Poland.

other common names

German: Schummels Inocelliide.

physical characteristics

Small to medium-sized species with forewings of 0.31–0.43 in (8–11 mm) in males and 0.41–0.59 in (10.5–15 mm) in females. Pterostigma is dark brown. The "rectangular" head and the lack of ocelli are typical for the family.

distribution

Central and northern Europe to eastern Asia.

habitat

Coniferous, particularly pine, forests from low elevations up to 3,280 ft (1,000 m).

behavior

Little is known, though females are clumsy flyers.

feeding ecology and diet

Larvae are found under the bark of conifers, particularly pines, feeding on soft-bodied arthropods. Adult diet is unknown but may consist of pollen.

reproductive biology

Life cycle is usually two to three years.

conservation status

Not listed by the IUCN. Rare but not threatened.

significance to humans

None known.

Brauer's inocelliid snakefly

Parainocellia braueri

family

Inocelliidae

taxonomy

Inocellia braueri Albarda, 1891, "Southern Europe."

other common names

German: Brauers Inocelliide.

physical characteristics

Small to medium-sized species with forewings of 0.27–0.34 in (7–8.7 mm) in males and 0.35–0.47 in (8.8–12 mm) in females. Characterized by a yellowish pattern on its otherwise black head.

distribution

Central and southeastern Europe.

habitat

Open deciduous forests in warm localities, from below 656 ft (200 m) in central Europe to more than 3,280 ft (1,000 m) in the southern-most parts of its range.

behavior

Larvae are sometimes found in high densities. Adults are poor flyers.

feeding ecology and diet

Larvae are found under the bark of various deciduous trees (pears, oaks, maples, etc.) feeding on soft-bodied arthropods. Adult diet is unknown but may consist of pollen.

reproductive biology

The life cycle is at least two and generally three to four years.

conservation status

Not listed by the IUCN, but rare and possibly threatened.

significance to humans

None known.

Schremmer's snakefly

Alena (Aztekoraphidia) schremmeri

family

Raphidiidae

taxonomy

Alena (Aztekoraphidia) schremmeri Aspöck, Aspöck, and Rausch, 1994, Sierra de Miahuatlán, Oaxaca, México.

other common names

German: Schremmers Kamelhalsfliege.

physical characteristics

Slender snakefly with forewings of 0.27–0.31 in (7–8 mm) in males and 0.31–0.37 in (8–9.5 mm) in females and a pterostigma that is mostly yellow but brown at its borders.

distribution

Known only from the mountain range of its type locality (Sierra de Miahuatlán, Oaxaca, México). This species has the southernmost-known distribution of any extant Raphidiid snakefly.

habitat

Inhabits pine forests from 6,235–6,890 ft (1,900–2,100 m).

behavior

Little is known aside from feeding ecology and reproductive biology.

feeding ecology and diet

Larvae live under bark and adults on trees, both feeding on soft-bodied arthropods.

reproductive biology

The life cycle lasts two years, with pupation and appearance of adults in spring or summer.

conservation status

Not listed by the IUCN. Although adults are encountered rarely, the species likely is not threatened.

significance to humans

Beneficial as a predator of pine-tree pests.

Yellow-footed snakefly

Dichrostigma flavipes

family

Raphidiidae

taxonomy

Raphidia flavipes Stein, 1863, Greece.

other common names

German: Gelbfuss-Kamelhalsfliege.

physical characteristics

A slim species with forewings of 0.31–0.52 in (8–13.3 mm) in males and 0.39–0.57 in (10–14.5 mm) in females. Characterized by a bicolored (proximally brown, distally yellow) pterostigma and (with the exception of the black coxae) predominantly yellow legs.

distribution

Central, eastern, and southeastern Europe.

habitat

Prefers warmer habitats, particularly open forests with scattered trees and shrubs.

behavior

Occasionally reaches swarm-like population densities on whitethorns.

feeding ecology and diet

Larvae are found under layers of soil around trees and bushes, while adults are found mainly on shrubs; both feed on softbodied arthropods.

reproductive biology

The life cycle lasts two years.

conservation status

Not listed by the IUCN. Common in many parts of Europe.

significance to humans

This was the first snakefly found to have soil-dwelling larvae.

Wart-headed Uzbekian snakefly

Mongoloraphidia (Usbekoraphidia) josifovi

family

Raphidiidae

taxonomy

Raphidia (Bureschiella) josifovi Popov, 1974, Kondara-Kwack, Gissarskij chrebet, Tajikistan.

other common names

German: Usbekische Warzenkopf-Kamelhalsfliege.

physical characteristics

This stout medium-sized species is characterized by the wartlike sculpture of its head.

distribution

Tajikistan and Uzbekistan.

habitat

Juniperus stands in mountainous areas from 4,595–6,890 ft (1,400–2,100 m) in elevation.

behavior

Little is known beside feeding ecology and reproductive biology.

feeding ecology and diet

Larvae are found predominantly under the bark of Juniperus and adults on twigs, both feeding on soft-bodied arthropods.

reproductive biology

Observed copulation follows the "wrecking position," in which the male hangs head first from the female, who carries him. The life cycle is at least two years.

conservation status

Not listed by the IUCN. Dependent on conservation of Juniperus.

significance to humans

None known.

Common European snakefly

Phaeostigma (Phaeostigma) notata

family

Raphidiidae

taxonomy

Raphidia notata Fabricius, 1781, Coombe Hurst, Croydon, Surrey, England.

other common names

German: Gemeine europäische Kamelhalsfliege.

physical characteristics

Robust snakefly with forewings of 0.35–0.51 in (9–13 mm) in males and 0.39–0.57 in (10–14.5 mm) in females and a dark brown pterostigma.

distribution

From Great Britain to northeastern Spain, including central and northern Europe as well as parts of eastern Europe.

habitat

Inhabits a wide range of coniferous and deciduous forests from low elevations to almost 6,560 ft (2,000 m).

behavior

The grooming behavior comprises a complex ritual of cleaning the head, antennae, mouthparts, and legs.

feeding ecology and diet

Larvae live under bark and adults on trees, and both feed on soft-bodied arthropods.

reproductive biology

The life cycle lasts either two or three years.

conservation status

Not listed by the IUCN. Rare but not threatened.

significance to humans

Beneficial to humans as a predator of pests.

Resources

Books

Aspöck, Horst, Ulrike Aspöck, and Hubert Rausch. Die Raphidiopteren der Erde. 2 vols. Krefeld, Germany: Goecke und Evers, 1991.

Tauber, Catherine A. "Order Raphidioptera." In Immature Insects, edited by Frederick W. Stehr. 2 vols. Dubuque, IA: Kendull/Hunt Publishing Company, 1987–1991.

Periodicals

Acker, Thomas S. "Courtship and Mating Behavior in Agulla species (Neuroptera: Raphidiidae)." Annals of the Entomological Society of America 59 (1966): 1–6.

Aspöck, Horst. "The Biology of Raphidioptera: A Review of Present Knowledge." Acta Zoologica Academiae Scientiarum Hungaricae 48 (2002): 35–50.

——. "Distribution and Biogeography of the Order Raphidioptera: Updated Facts and a New Hypothesis." Zoologica Fennica 209 (1998): 33–44.

Kovarik, Peter W., Horace R. Burke, and Charles W. Agnew. "Development and Behavior of a Snakefly, Raphidia bicolor Albarda (Neuroptera: Raphidiidae)." Southwestern Entomologist 16 (1991): 353–364.

Organizations

IAN: International Association of Neuropterology. Web site: <http://www.neuroptera.com>

Other

Oswald, John D. "Bibliography of the Neuropterida." 2003 [May 8, 2003]. <http://entowww.tamu.edu/research/neuropterida/neur_bibliography/bibhome.html>.

Ulrike Aspöck, PhD

Horst Aspöck, PhD

Hubert Rausch