Ammotrechidae

Distinguished from other solifuge families by: (1) absence of claws on tarsi of leg I; (2) tarsal segmentation pattern 1-2-2-(2-4); (3) pedipalps bearing pairs of lateroventral spines; (4) males with immovable flagellum on mesal face of each chelicera; and (5) recurved propeltidium. The recurved facial profile is particularly distinctive and provides the common name "curve-faced solifugids." In North America, only Eremobatidae co-occurs; Ammotrechidae can be separated by the above characters, particularly the recurved propeltidium versus the flattened propeltidium of Eremobatidae.

Medium-sized arachnids, with North American species rarely exceeding 2 inches in length. The propeltidium (dorsal plate of the prosoma) is distinctly recurved, creating a concave facial profile. Chelicerae are massive, comprising up to one-third of body length in some species, with toothed fixed and movable fingers forming powerful nutcracker-like jaws. Pedipalps are long, stout, and bear pairs of lateroventral spines; they are tipped with suctorial organs for climbing and prey manipulation. The body is covered in fine insulating hairs with sparse longer setae serving as tactile sensors. Tarsal segmentation is 1-2-2-(2-4). Leg I tarsi lack claws. Males possess an immovable flagellum on the mesal face of each chelicera.

Arid and semi-arid regions including sand dunes, rocky habitats, and desert scrub. In North America, primarily found in the southwestern United States from southern California through Arizona, New Mexico, and Texas. Some species occupy coastal mangrove forests in the Caribbean and northern South America, showing tolerance to higher humidity and saline conditions. Microhabitats include fallen trees, decomposed wood, and floodable areas with specific height preferences (0.5–2.7 m above ground). Both males and females construct shallow burrows for protection from daytime heat and for nesting.

Western Hemisphere distribution encompassing North America, Central America, South America, and Caribbean Islands. In North America, concentrated in the South and Southwest. South American records include Argentina (Patagonia and Monte desert regions), Chile, Colombia, and Brazil. Caribbean occurrences include mangrove forest habitats. The family is one of only two solifuge families present in North America (with Eremobatidae).

Primarily nocturnal, with most North American species active at night. Can be found around outdoor lights where they prey on fallen insects. Some species active by day, accounting for the alternative common name "sun spiders." Daytime refuge sought under boards, flat stones, cow patties, and within self-constructed burrows.

Carnivorous, feeding on other invertebrates including insects, spiders, scorpions, and termites. Prey is masticated mechanically using the powerful chelicerae; liquids are then sucked out. Prey detection occurs through malleoli (chemosensory racket organs on hind legs) combined with tapping movements of pedipalps, allowing detection of subterranean prey at shallow depths. Cannibalism has been documented within the family.

Developmental stages include egg, post-embryo, nymphal instars, and adult. Females lay eggs in burrows. Specific details of instar number and duration not documented for the family as a whole. Adults require their full lifespan to locate mates and reproduce.

Extremely fast runners, capable of sprinting at approximately 53 cm/second for short bursts, using only six of eight legs for locomotion while the first pair serves sensory functions. Highly agile, capable of rapid directional changes that make capture difficult. When cornered, individuals may rear up while waving pedipalps and first leg pair menacingly, with chelicerae open. Mating involves complex courtship including an "attack phase" that resembles aggression; males grasp females with chelicerae and stroke with pedipalps and first legs. In Oltacola chacoensis, males employ sexual coercion (forced copulation) while simultaneously performing copulatory courtship (pedipalp tapping), demonstrating that coercion and luring behaviors can coexist. Females of some species resist by continuous body shaking and chelicerae opening.

Predators in arid food webs, consuming pest arthropods including scorpions, spiders, and termites. Serve as prey for vertebrates. Their high metabolic rates support rapid prey consumption and population turnover. In mangrove ecosystems, occurrence is tied to microhabitat availability that provides shelter and nesting sites.

Generally beneficial due to predation on pest arthropods including scorpions, spiders, and termites. Occasionally considered pests when entering human dwellings but pose no medical threat—lacking venom and rarely biting unless provoked. Non-venomous bites are mechanically painful but harmless. Subject to extensive misinformation and urban legends, particularly regarding Middle Eastern species, but North American species are smaller and less aggressive than folklore suggests. Not recommended as pets due to frenetic activity and specialized habitat requirements.

• EremobatidaeOnly other solifuge family in North America; distinguished by flattened (not recurved) propeltidium, presence of claws on leg I tarsi, and different tarsal segmentation and pedipalp spine patterns

Subject to numerous false claims including: reaching dinner-plate sizes (North American species rarely exceed 2 inches); running at 25 mph while screaming (actual sprint speed ~53 cm/second, silent); eating camel stomachs or sleeping soldiers' faces (no evidence); and being venomous (completely non-venomous, relying on mechanical damage from chelicerae). These myths originated primarily from U.S. military personnel in the Middle East and persist despite thorough debunking.

• BugGuide
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• GBIF taxonomy match
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• NCBI Taxonomy
• Catalogue of Life
• Insect FAQs | Entomology Research Museum
• Bug Eric: Desert Demon, the Solifuge
• Bug Eric: August 2010
• Ecological aspects of Ammotrechella manggi (Solifugae: Ammotrechidae) in mangrove forest from southern Morrosquillo Gulf, Colombian Caribbean
• Sexual coercion does not exclude luring behavior in the climbing camel-spider Oltacola chacoensis (Arachnida, Solifugae, Ammotrechidae)
• The genus Pseudocleobis Pocock, 1900 (Solifugae: Ammotrechidae) in transitional Patagonia-Monte deserts, with descriptions of two new species
• Revision of the genera Eutrecha and Xenotrecha (Solifugae: Ammotrechidae), taxonomic notes on Ammotrechinae, and description of a remarkable new Eutrecha from Colombia
• Chileotrecha romero (Kraus, 1966) comb. nov. and Pseudocleobis patagonicus (Roewer, 1934) comb. nov. transferral from Mummuciidae to Ammotrechidae (Arachnida, Solifugae)
• Unveiling high solifuge diversity: Review of the genus Pseudocleobis Pocock, 1900 (Ammotrechidae) in Chile with the description of nine new species.