Solifuge, tropical spider with many species!


Photo credit: Bernard Dupont

Very widespread in tropical and subtropical regions, solifuges however prefer to live in arid or semi-desert environments. To escape the extreme heat, the thousand species recorded on the planet live at night and take refuge in burrows. The particularity of solifuges, however, lies in their large chelicerae which form shredding pincers equipped with teeth. If the bites of larger specimens can perforate the skin, it is rare for a human to come across this fierce and nocturnal arachnid. Portrait of solifuges, these numerous arachnids that are also nicknamed false spiders.

Who are the solifuges?

Solifuges constitute an order of arthropods of the class Arachnids. The more than 1000 species known to date live mainly in the tropical and subtropical countries of the planet. Their name, from the Latin “solifuga”, means “which flees the sun” (from sol, sun and fugere, to flee). Many nicknames are given to solifuges such as the sun spider, the wind scorpion, the 10-legged spider or the false spider. Solifuges are divided into 13 families:

Ammotrechidae; Ceromidae; Daesiidae; Eremobatidae; Galeodidae; Gylippidae; Hexisopodidae; Karschiidae; Melanoblossiidae; Mummuciidae; Protosolpugidae; Rhagodidae; Solpugidae. Why are solifuges called “false spiders”?

Solifuges are often called “false spiders” because of their resemblance to “real” spiders. These 2 invertebrates belong to the class of arachnids and share several characteristics but there are profound differences. Some examples :

Within the class of arachnids, solifuges form a distinct order called Solifugae while spiders belong to the order Araneae; Solifuges have a cephalothorax fused with an abdomen, unlike spiders which have a body divided into 2 very distinct parts; Unlike many spiders, solifuges do not produce venom or silk (used in building webs, for moving, or for wrapping prey). How to recognize solifuges?

The size of the solifuges varies from one species to another: for example, between 0.6 and 7 cm for Solpugidae and 0.4 to 2 cm for Ammotrechidae. The body of solifuges is divided into 2 segments called prosoma (where the legs are inserted) and opisthosoma (tail). We observe a slight narrowing between these 2 parts (not as pronounced as in spiders), hence the impression of a more homogeneous and long silhouette. Solifuges have 8 legs but with their 2 imposing pedipalps located at the front of the body, they appear to have 10. These 2 long appendages are located near the mouth and are used to manipulate food and explore their environment. They often remain raised like antennas, and are extremely sensitive. The sticky tip of the pedipalps allows solifuges to easily climb walls and thus benefit from great mobility. A particularity of these arachnids lies in their 2 large and powerful chelicerae at the mouth which help them to feed. Each of the chelicerae is made up of 2 pincer-shaped articles with teeth. The 3 pairs of hind legs of the solifuge are used for locomotion.

What are solifuge hairs used for?

Solifuges have fine hairs that vary in density depending on the species. These hairs can cover the entire surface of the body, including the cephalothorax, abdomen, legs and other appendages. These sensory attributes help solifuges explore their environment, feel vibrations, detect movements, changes in the air. This extreme sensitivity allows them to locate prey and spot danger such as the arrival of a predator. The hairs of solifuges may also play a role in communication between conspecifics through tactile signals during social interactions or at the time of reproduction.

Where do solifuges live?

Solifuges are distributed almost everywhere on the planet, from warm countries to temperate zones, both in the plains and at altitude, up to 3,000 m in the Turkestan mountains. The largest species live in tropical and subtropical regions and especially in the semi-arid to desert zones of Africa and Asia. These arachnids are also found in greener areas and forests. The family Daesiidae, for example, is widely distributed in Africa while Rhagodidae is present in Australia and parts of Asia. Melanoblossiidae occupy southern Africa only and Mummuciidae occupy only South America. We can find solifuges of modest size in Europe, such as the species Galeodes caspius in Greece and Spain, but none lives in France.

What do solifuges eat?

These exclusively carnivorous species feed on insects, especially flies, bedbugs, termites, ladybugs, bees and other small arthropods. However, some large species can attack scorpions, toads, lizards, small rodents (mice) and birds. Solifuges are known to be lively and fast hunters (some specimens can exceed 15 km/h top speed). These arachnids are mostly opportunistic predators that actively hunt rather than passively wait. The adhesive ends of their pedipalps facilitate the capture of prey which the solifuges then carry to their chelicerae to crush them. After grabbing their victim, the arachnids release digestive juices containing powerful enzymes that break down animal tissues. All that remains for the solifuge is to suck up the liquids resulting from this chemical decomposition through its oral apparatus.

How do solifuges live?

Solifuges are mainly active between May and November. Although they appreciate arid areas, these nocturnal species avoid light and high heat to minimize water loss. Solifuges have the habit of digging burrows with their chelicerae and legs to protect themselves from the high temperatures that characterize their natural habitat. Arachnids can also invade mammal galleries to avoid digging efforts. In winter, solifuges take refuge in a shelter underground or bury themselves under the sand to warm up. Despite their appearance, these arthropods lack venom glands and are harmless to humans. The bites of larger species are likely to perforate human skin, but solifuges only show aggression if they feel threatened. Considering their nocturnal lifestyle, it is exceptional to cross their path.

How do solifuges reproduce?

Solifuges only reproduce once in their life. Sperm transfer can be done directly or indirectly. In the first case, the male deposits his gametes on the ground and collects them with his pedipalps and then transfers them to his partner. In the second case, it produces a spermatophore, places it in the genital tract of the female who can store it and delay fertilization. The clutch consists of between 50 and 200 eggs that the mother places in a shallow hole that she has dug on the ground, in the sand or another suitable substrate. When some species immediately abandon their nest, others watch over the brood until they hatch, which can take 1 month. Once hatched, the larvae go through several stages of development (around 9 molts) before reaching adulthood. The female dies approximately 6 weeks after laying eggs while the male perishes shortly after mating. Solifuges rarely live more than 1 year.

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