Solifugea
Solifugea is an order of arachnids native to arid areas around the world. They are sometimes referred to as Sun-Spiders, Wind-spiders, Barrel-spiders, False-spiders, Wind-scorpions, or Camel-spiders.[4][6] There are many more local names in addition to these. Despite their close resemblance to spiders, they are actually a completely separate order.
Taxonomy
Solifugea is an order contained within the class Arachnida and the phylum Arthropoda. Within Solifugae there are 12 families, 141 genera, and approximately 1,087 described species.[4] the first one was described in 1772 by Pallas. They are commonly considered a sister group to Pseudoscorpions and both are placed in the clade Haplocnemata.[4][6]
Morphology
Spider-like in their appearance they can be differentiated by their oversized chelicerae and pedipalp, giving the appearance of a fifth set of legs. Those are used to grab and tear apart prey.[6] Adults range in size from 1 to 7 cm, but the largest has a leg span of 12cm.[4][6] They have a series of fan-shaped structures underneath their fourth pair of legs referred to as racquet organs. These are believed to be used in chemoreception.[6] They are not venomous but can deliver a serious bite. Their body is divided into two sections, the carapace, and the abdomen. The abdomen is expandable to allow them to eat large amounts of food.[8] They also possess a unique suctorial organ that allows them to stick directly to even extremely smooth surfaces like glass. This organ is extendable and contains microscopic ridges that allow for suction.[2][7] Solifuges start their life as non-motile larvae, this lasts 1-3 days before they molt into 1 instar nymphs. Starting in the II instar, nymphs are epigeic predators. There are 4 to 10 instar phases depending on species. [1] Solifugae are characterized by their unusual mode of reproduction in which the male will lay the spermatophore on the soil surface which is then transferred to the female manually using its chelicerae.[7] North American species do not use this method.[2] The female will then dig a burrow and lay her eggs, 30 to 200 depending on the species. They are characterized by univoltine development, meaning only one generation develops each year, but some species are known to be bivoltine.[1]
Range and habitat
The presence of Solifugae is considered an indicator species of desert biomes. The range is restricted to warm dry areas with little vegetation.[5] They are found in tropical and subtropical deserts in Africa, Asia, the Americas, the Middle East, and southern Europe.[2]
Ecology
In most environments solifuges are only active in the summer, spending the cold season hibernating in burrows. Active adults have a short lifetime, appearing in only the final two to five weeks of summer. They are primarily nocturnal, with some species being exceptions to this. [1] There is evidence that some species of Solifugae will share burrows with prairie dogs in the American southwest. The exact reasons for this are unknown but it is suspected that it has something to do with greater abundance in arthropods caused by the management of prairie dogs.[3] They are voracious predators that hunt by chasing down their prey. They have two adaptations that make them highly capable of sustained high-speed running. Firstly, unlike most arachnids, they lack a book lung, instead, using a tracheal system for respiration which is much more efficient for oxygen uptake. Secondly, they run on only six of their legs, combined with their long legs and unique joint structure allow them to maximize their stride and agility.[2] They mainly hunt insects, spiders, and scorpions. There are however larger species that are known to hunt small lizards, mammals, and birds.[6] some species are exclusively termite predators.[8] They will attack humans and other large animals if provoked and are known to be capable of inflicting severe wounds. Like scorpions they fluoresce under UV light, this is one of the most useful methods to capture them.[8]
References
[1] Belozerov, V. N. 2013. Seasonal aspects of the life cycle of solifugae (Arachnida, Solifugae) as compared with pseudoscorpions (Arachnida, Pseudoscorpiones). Entomological Review 93:1050–1073.
[2] Cowles, J. 2018. Wind Spiders:: Solifugae. Pages 114–123 Amazing Arachnids. Princeton University Press.
[3] Duval, B. D., and W. G. Whitford. 2009. Camel Spider (Solifugae) Use of Prairie Dog Colonies. Western North American Naturalist 69:272–276.
[4] Harvey, M. S. 2002. The Neglected Cousins: What Do We Know about the Smaller Arachnid Orders? The Journal of Arachnology 30:357–372.
[5] Institute of Zoology of National Academy of Sciences of Azerbaijan, and N. E. Novruzov. 2017. Comparison of trophic spectra and hunting strategies of some large arachnids (Arachnida: Scorpiones, Solifugae, Aranei) in semi-desert biocenoses of Gobustan (Eastern Azerbaijan). Caucasian Entomological Bulletin 13:135–144.
[6] Mullen, G. R., L. A. Durden, and G. Mullen. 2002. Medical and Veterinary Entomology. Elsevier Science & Technology, Burlington, UNITED STATES.
[7] Solifugae - an overview | ScienceDirect Topics. (n.d.). . https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/solifugae.
[8] Solifugae (solifuges, solifugids, solpugids). (n.d.). . http://www.biodiversityexplorer.info/arachnids/solifugids/index.htm.