Solifugae

Solifugae
A male Galeodes sp. (From R A Lydekker, 1879)
A male Galeodes sp. (From R A Lydekker, 1879)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Solifugae
Sundevall, 1833
Families

see text

Solifugae is an order of Arachnida, containing more than 1,000 described species in about 140 genera. The name derives from Latin, and means those that flee from the sun. The order is also known by the names Solpugida, Solpugides, Solpugae, Galeodea and Mycetophorae. Their common names include camel spider, wind scorpion, sun scorpion and sun spider.

Solifugae are not true spiders, which are from a different order, Araneae. Like scorpions and harvestmen, they belong to a distinct arachnid order.

Contents

Habitat

A Solifugid in Gobi Desert, Mongolia

Most Solifugae inhabit warm and arid habitats, including virtually all deserts in both the Eastern and Western Hemispheres, excluding Australia[1]. Some species have been known to live in grassland or forest habitats. The most distinctive feature of Solifugae is their large chelicerae. Each of the two chelicerae are composed of two articles forming a powerful pincer; each article bears a variable number of teeth. Solifugae also have long pedipalps, which function as sense organs similar to insects' antennae and give the appearance of the two extra legs. Pedipalps terminate in eversible adhesive organs. These are used to capture flying prey, and for climbing. They stridulate with their chelicerae, resulting in a rattling noise[1].

Diet

Solifugae are carnivorous or omnivorous, with most species feeding on termites, darkling beetles, and other small arthropods, although Solifugae have been videotaped consuming larger prey such as lizards. Prey is located with the pedipalps and killed and cut into pieces by the chelicerae. The prey is then liquefied and the liquid ingested through the pharynx. Although they do not normally attack humans, these chelicerae can penetrate human skin, and painful bites have been reported.[1]

Reproduction

Reproduction can involve direct or indirect sperm transfer; when indirect, the male emits a spermatophore on the ground and then inserts it with his chelicerae in the female's genital pore. To do this, he flings the female on its back. The female then digs a burrow, into which it lays 50 to 200 eggs, depending on the species. These are guarded until they hatch. Because the female will not feed during this time, it will try to fatten itself beforehand, and a species of 5 cm has been observed to eat more than 100 flies during that time in the laboratory.[1]

Anatomy

Like pseudoscorpions and harvestmen, they lack book lungs. In some species there are very large central eyes that are capable of recognizing forms, these are used for hunting. Lateral eyes are only rudimentary or lacking. Males are usually smaller than females, with longer legs.[1]

Behavior

As indicated by the origin of their name, Solifugae are mostly nocturnal, and seek shade during the day. It was this behaviour which led coalition soldiers in the 2003 invasion of Iraq to think these arachnids were attacking them. In reality, they were merely moving toward the newly available shade provided by the soldiers' presence. The absence of shade sends them away.

Urban legends

A Solifugid

Solifugae are the subject of many urban legends and exaggerations about their size, speed, behavior, appetite, and lethality. They are not especially large, the biggest having a leg span of perhaps 12 centimeters (5 in)[1]. They are fast on land compared to other invertebrates, the fastest can run perhaps 16 kilometers per hour (10 mph), nearly half as fast as the fastest human sprinter. Members of this order of Arachnida apparently have no venom, with the possible exception of one species in India (see below) and do not spin webs.

In the Middle East, it is widely rumored among American and coalition military forces stationed there that Solifugae will feed on living human flesh. The story goes that the creature will inject some anaesthetizing venom into the exposed skin of its sleeping victim, then feed voraciously, leaving the victim to awaken with a gaping wound. Solifugae, however, do not produce such an anaesthetic, and they do not attack prey larger than themselves unless threatened. Other stories include tales of them leaping into the air, disemboweling camels, screaming, and running alongside moving humvees; all of these tales are dubious at best. Due to their bizarre appearance many people are startled or even afraid of them. This fear was sufficient to drive a family from their home when one was discovered in a soldier's house in Colchester [2]. The greatest threat they pose to humans, however, is their bite in self-defense when one tries to handle them. There is essentially no chance of death directly caused by the bite, but, due to the strong muscles of their chelicerae, they can produce a proportionately large, ragged wound that is prone to infection.

Venom controversy

While the absence of venom in Solifugae is a long-established fact[1], there is a single published study of one species, Rhagodes nigrocinctus, carried out in India in 1978 by a pair of researchers who did histological preparations of the chelicerae, and found what they believed to be epidermal glands[3]. Extracts from these glands were then injected into lizards, where it induced paralysis in 7 of 10 tests. While this study has never been confirmed, and while other researchers have been unable to locate similar glands in other species, this particular species does appear to possess venom, although it is not known if there is any mechanism for introducing it into prey (recall that the researchers manually injected it into lizards).

Classification

There are twelve families belonging to the order Solifugae:

The family Protosolpugidae is only known from one fossil species from the Pennsylvanian.

Gallery

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Schmidt, G. (1993) Giftige und gefährliche Spinnentiere. Westarp Wissenschaften ISBN 3894324058
  2. ↑ "Spider forces family out of home", BBC News, 2008-08-28, http://www.cnn.com/2008/WORLD/europe/08/28/uk.dangerous.spider/index.html, retrieved on 2008-08-28 
  3. ↑ Aruchami, M. & Sundara Rajulu, G. (1978) An investigation on the poison glands and the nature of the venom of Rhagodes nigrocinctus (Solifugae: Arachnida). Nat. Acad. Sci. Letters (India) 1: 191-192.

External links