Olios

Distinguished from other Sparassidae genera by eye arrangement (eight eyes in two partially straight rows) and male palpal morphology used to define species groups. The genus is divided into eight species groups (argelasius-, coenobitus-, auricomis-, correvoni-, rossettii-, nentwigi-, stimulator-, and hirtus-groups) based on detailed morphological characters. O. giganteus in North America was formerly misidentified as O. fasciculatus (an African species). Species-level identification requires examination of genitalia and other detailed morphological features.

Small to large-bodied sparassid spiders with eight eyes in two partially straight rows. Smaller species typically light brown to brown with darker markings; larger species generally darker, with some members exhibiting green coloration. Legs are laterigrade (twisted at the base, oriented horizontally), allowing the flat body to enter narrow crevices. Paired claws at leg tips with tuft of special hairs between them enable navigation of textured surfaces. Body size varies considerably: O. giganteus females reach 14.6-48 mm body length (average 31.6 mm), males 11.3-29.4 mm (average 25 mm), with legspan 50-64 mm.

Highly varied due to wide distribution: savannahs, rainforests, dry mixed conifer forests, parklands, and urban areas. Primarily found in vegetation including trees, under loose bark, and on vertical surfaces. Occasionally found in human structures. O. biprocessus collected under bark at 30m elevation; O. uniprocessus found in urban setting at 253m elevation; O. lincangensis from high-elevation mountain habitat at 3428m. Rarely found in houses, though sometimes inadvertently transported with fruit shipments.

Global distribution concentrated in tropical and subtropical regions. Primary regions: Africa (widespread including Mediterranean region, northern Africa, sub-Saharan Africa, Madagascar), southern Europe, Asia (Middle East, Central Asia, South Asia, East Asia, Southeast Asia, Indonesia, Philippines), and scattered occurrences in North America (southwestern U.S. from California to western Texas, introduced). Specific species groups have more restricted ranges: argelasius-group (Mediterranean, northern Africa, Canary Islands, Middle East, South Sudan, East Africa, southern Africa); coenobitus-group (Gambia, Angola, Tanzania, Madagascar, India, Sri Lanka, Java); auricomis-group (Africa south of 10°N); rossettii-group (Mediterranean, eastern Africa, Asia from Middle East to Japan, Philippines, Java); nentwigi-group (Southeast Asia, China, Taiwan, Indonesia, Philippines, Papua New Guinea, Mariana Islands); stimulator-group (Madagascar, Seychelles, Middle East, South Asia); hirtus-group (South, East and Southeast Asia).

Nocturnal hunters active at night. In North America, egg incubation occurs mid-late summer (approximately one month).

Insectivorous. Prey consists of insects.

Females normally nomadic but become sedentary when gravid. They construct large bag-like retreats within which they spin egg sacs. Females guard egg sacs and emerging spiderlings throughout incubation period, not feeding during this time. Spiderlings emerge after approximately one month. Little additional information available on developmental stages or longevity.

Nocturnal hunters that hide by day and emerge at night to pursue prey. Capable of rapid movement and agile climbing on vertical surfaces and slender twigs due to specialized leg structure. Can navigate slick surfaces and enter very narrow cracks or crevices. O. giganteus has been observed to enter buildings. Females exhibit maternal care of egg sacs and young.

Predator of insects. May influence local arthropod community structure through predation. One observer noted reduced scorpion presence when Olios spiders were active nearby.

Bites not considered dangerous to humans; venom used primarily to subdue prey. Bite symptoms may include mild redness, swelling, or pain comparable to a bee sting. Occasionally encountered indoors, causing alarm due to large size. Sometimes inadvertently transported with tropical fruit shipments. Historical newspaper publicity referred to them as "barking spiders" in some west Texas towns. Some species kept as biocontrol agents for insect pests in homes.

• Other Sparassidae genera (e.g., Heteropoda, Palystes)Share family characteristics including large size and laterigrade legs, but distinguished by eye arrangement and male genital morphology
• Thomisidae (crab spiders)Similar common name and laterigrade leg structure, but different family with different eye arrangement and hunting behavior
• Philodromidae (running crab spiders)Similar leg orientation and habitat use, but smaller size and different eye arrangement
• Selenopidae (wall crab spiders)Similar flattened body and crevice-dwelling habit, but different eye arrangement and geographic distribution

O. giganteus in North America was long misidentified as O. fasciculatus, an African species. The "barking spider" name applied to some populations appears to be a local colloquialism rather than a formal common name. Many species historically placed in Olios have been transferred to other genera or recognized as misplaced in the subfamilies Deleninae, Sparassinae, and Palystinae.

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Spider Sunday: Giant Crab Spider
• Bug Eric: New Mexico Night Bugs
• Three new species of the genus Olios Walckenaer, 1837 (Araneae, Sparassidae) from southern China
• The spider genus Olios Walckenaer, 1837 (Araneae: Sparassidae)—Part 1: species groups, diagnoses, identification keys, distribution maps and revision of the argelasius-, coenobitus- and auricomis-groups