Camel spiders are arthropods belonging to the order Solifugae within the class Arachnida. They are also referred to as solifuges, sun spiders, wind scorpions, or scorpion carriers. They derive their name from their shared desert habitat with camels. Some sources also suggest that the hump-like shape of their prosoma (the front part of their body), which resemble a camel’s hump, inspire the name. The order name ‘Solifugae’ is derived from the Latin words sol and fugere, which roughly translates to ‘sun’ and ‘to flee’ or ‘to escape.’
Despite the common names, they are neither true spiders (order Araneae) nor scorpions (order Scorpiones), although they share some morphological features with them. For instance, these arachnids have a distinctly hairy, spider-like appearance and possess large, powerful chelicerae (jaws) that resemble scorpion pincers.
Over 1,200 described species of camel spiders are grouped under 16 families and 146 genera, many of which are still under study[1][2].
Camel spiders range in size from just a few millimeters up to several centimeters in body length (including their legs), with the largest species typically reaching 12–15 cm (5–6 in). However, this measurement can vary due to differences in leg length across different species. A more accurate depiction of their size is thus obtained by considering the body length alone, which can extend up to 7 cm (~ 3 in). Though most species measure around 5 cm (~2 in), some reach up to 7 cm (~3 in), while smaller species may mature at under 1 cm (0.4 in).
Sexual dimorphism is prominent in them, with the males having smaller body sizes but proportionally longer legs than the females. Another distinctive characteristic of males is the presence of a pair of flagella (also called horns) on each chelicera[3], which are believed to have a reproductive significance. However, their exact function remains unclear.
Similar to spiders (Araneae), their body is divided into two primary tagmata: the anterior ‘prosoma’ (cephalothorax) and the posterior ‘opisthosoma’ (10-segmented abdomen)[3]. Unlike spiders, however, these arachnids lack the pedicel, a narrow connecting tube between the body segments, indicating an evolutionary divergence between Solifugae and Araneae.
The prosoma comprises the head, mouthparts, and somites that bear the legs and pedipalps and is encased by a carapace, also called a prosomal dorsal shield or ‘peltidium,’ which protects the prosoma. The carapace is divided into three distinct segments: the propeltidium, mesopeltidium, and metapeltidium. The propeltidium houses the eyes, conspicuously large chelicerae (for feeding), pedipalps (for sensory reception), and the first two pairs of legs. The meso- and metapeltidium segments accommodate the remaining leg pairs. Unlike scorpions, camel spiders lack the third tagma that usually forms a tail.
These jaw-like mouthparts are one of the most striking features of camel spiders, justifying their classification under the subphylum Chelicerata. These chelicerae are bifurcated into two segments (parts connected by joints), forming a powerful pincer, resembling those of crabs. Depending on the species, these segments bear a variable number of teeth for feeding.
Although they appear to have five pairs of legs, only the four pairs of posterior legs are true legs. The first pair of appendages, often mistaken for legs, are actually ‘pedipalps,’ each consisting of five segments. Each posterior pair of legs is divided into seven parts: coxa, trochanter, femur, patella, tibia, metatarsus, and tarsus. The first pair of true legs is smaller and thinner than the three posterior pairs, assisting in sensory perception along with the pedipalps. Primarily, the posterior three pairs of legs are used in locomotion. Some camel spiders feature specialized sensory structures called ‘malleoli’ or ‘racquet organs’ on the ventral surfaces of the coxae and trochanters of the last pair of legs.
They have a pair of large central eyes known as median ocelli (simple eyes) that are significantly more developed for hunting and locating enemies. Together with median eyes, camel spiders possess a pair of non-functional lateral ocelli. The presence of well-developed median ocelli suggests an intermediate evolutionary stage between simple ocelli and more complex eye structures.
Unlike most arachnids from the orders of scorpions and Tetrapulmonata, Solifugae do not possess book lungs. Instead, they feature an advanced tracheal system for respiration, drawing in and expelling air through multiple spiracles. Specifically, they have one pair of spiracles between the second and third pairs of walking legs, two pairs situated on the third and fourth abdominal segments, and a single, unpaired spiracle on the fifth abdominal segment[4]. Solifugae possess opisthosomal protuberances that resemble the respiratory sacs found in palpigrades, a group of minute, enigmatic arachnids known for their distinct respiratory structures during embryonic development.
In 2023, a groundbreaking phylogenomics study provided a clear picture of Solifugae’s family tree, showing two primary branches or suborders: Boreosolifugae and Australosolifugae. Daesiidae and Ammotrechidae were confirmed to be monophyletic. The family Melanoblossidae was nested within Daesiidae, and Mummuciidae within Ammotrechidae.
This nuanced phylogenetic classification, along with the geographic spread of camel spider families across both hemispheres, supports the idea that Australosolifugae likely originated from the southern supercontinent Gondwana, while Boreosolifugae came from the northern supercontinent Laurasia.
According to the World Solifugae Catalog, camel spiders are distributed under the following suborders and families.
These arachnids are mainly found in arid and semi-arid regions, such as the Sahara in Africa, the Sonoran and Mojave Deserts in North America, and the Arabian Peninsula and Middle East in Asia. They are not found in Antarctica or Australia.
They usually thrive in sandy habitats with high temperatures, low humidity, and minimal vegetation. While most common in desert biomes, they also inhabit semi-deserts, grasslands, scrubs, and forests.
Camel spiders are opportunistic carnivores that primarily feed on arthropods, such as termites and darkling beetles, and occasionally on small vertebrates like lizards and rodents[5]. Sometimes, they also hunt snakes, small lizards, and possibly young birds, though such behavior is not well-documented.
Camel spiders have a short lifespan of around 1 to 2 years.
These animals are univoltine, reproducing only once a year. The males and females gather during mating, and reproduction occurs either by direct or indirect sperm transfer.
In families like Galeodidae, the males use specialized structures called ‘modified palps’ or ‘embolus’ to transfer sperm directly into the female’s genital opening. Whereas in Solpugidae, the male deposits a spermatophore (capsule containing sperm) on the ground and guides the female to pick it up using her gonopods (appendages specialized for reproduction). The female later uses the stored sperm to fertilize her eggs during oviposition.
About 50 to 200 eggs are laid and stored in burrows dug by the mother for protection against predators[6]. She cautiously guards her eggs until they are ready to hatch in a few weeks. This young spider goes through 9 to 10 growth stages, known as instars, during which it repeatedly sheds its outer layer, or exoskeleton, until it reaches adulthood.
Camel spiders are preyed upon by scorpions, toads, large spiders, and, on rare occasions, bats. Human activities also pose a significant threat due to habitat destruction.
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