Huntsman spiders, members of the familySparassidae (formerly Heteropodidae), are known by this name because of their speed and mode of hunting.[citation needed] They are also called giant crab spiders because of their size and appearance. Larger species sometimes are referred to as wood spiders, because of their preference for woody places (forests, mine shafts, woodpiles, wooden shacks). In southern Africa the genus Palystes are known as rain spidersorlizard-eating spiders.[3] Commonly, they are confused with baboon spiders from the Mygalomorphaeinfraorder, which are not closely related.
Sparassids are eight-eyed spiders. The eyes appear in two largely forward-facing rows of four on the anterior aspect of the prosoma. Many species grow very large – in Laos, male giant huntsman spiders (Heteropoda maxima) attain a legspan of 25–30 centimetres (9.8–11.8 in). People unfamiliar with spider taxonomy commonly confuse large species with tarantulas, but huntsman spiders can generally be identified by their legs, which, rather than being jointed vertically relative to the body, are twisted in such a way that in some attitudes the legs extend forward in a crab-like fashion.[5] It is also commonly confused for a brown recluse spider, due to their shared coloring. However, brown recluse venom is significantly dangerous to humans, while that of the huntsman spider is less so.[6]
On their upper surfaces the main colours of huntsman spiders are inconspicuous shades of brown or grey, but many species have undersides more or less aposematically marked in black-and-white.[7] Their legs bear fairly prominent spines, but the rest of their bodies are smoothly furry. They tend to live under rocks, bark and similar shelters, but human encounters are common in sheds, garages and other infrequently-disturbed places. The banded huntsman (Holconia) is large, grey to brown with striped bands on its legs. The badge huntsman (Neosparassus) is larger still, brown and hairy. The tropical or brown huntsman (Heteropoda) is also large and hairy, with mottled brown, white and black markings. The eyesight of these spiders is not as good as that of the Salticidae (jumping spiders). Nevertheless, their vision is quite sufficient to detect approaching humans or other large animals from some distance.
They can be distinguished from other spider families by their appearance, as other spiders similar to them are smaller in size. They are often confused for tarantulas due to their hairy nature, but can easily be distinguished by their laterigrade legs, similar to those of crabs. Members of this family are also typically less bulky than tarantulas. They possess two claws, as is the case for most spiders that actively hunt their prey.[8] If this is not enough to fully identify them, they also possess eight eyes divided into two regular rows.[9]
On average, a huntsman spider's leg-span can reach up to 15 cm (5.9 in), while their bodies measure about 1.8 cm (0.7 in) long.[10] Like most spiders,[11] Sparassidae use venom to immobilize prey.
There have been reports of members of various genera such as Palystes,[12]Neosparassus and several others inflicting severe bites on humans. The effects vary, including local swelling and pain, nausea, headache, vomiting, irregular pulse rate, and heart palpitations, indicating some systemic neurological toxin effects, especially when the bites were severe or repeated. However, the formal study of spider bites is fraught with complications, including unpredictable infections, dry bites, shock, nocebo effects, and even bite misdiagnosis by medical professionals and specimen misidentification by the general public.[citation needed]
It is not always clear what provokes Sparassidae to attack and bite humans and animals, but it is known that female members of this family will aggressively defend their egg-sacs and young against perceived threats.[4] Bites from sparassids usually do not require hospital treatment.[citation needed]
Males of the huntsman spider Heteropoda venatoria have recently been found to deliberately make a substrate-borne sound when they detect a chemical (pheromone) left by a nearby female of their species. The males anchor themselves firmly to the surface onto which they have crawled and then use their legs to transmit vibrations from their bodies to the surface. Most of the sound emitted is produced by strong vibrations of the abdomen. The characteristic frequency of vibration and the pattern of bursts of sound identify them to females of their species, who will approach if they are interested in mating. This sound can often be heard as a rhythmic ticking, somewhat like a quartz clock, which fades in and out and can be heard by human ears in a relatively quiet environment.[13]
Members of the Sparassidae are native to tropical and warm temperate regions worldwide. A few species are native to colder climates, like the green huntsman spider (Micrommata virescens) which is native to Northern and Central Europe.[15] Some tropical species like Heteropoda venatoria (Cane huntsman) and Delena cancerides (Social huntsman) have been accidentally introduced to many subtropical parts of the world, including New Zealand (which has no native sparassid species).[16]
As adults, huntsman spiders do not build webs, but hunt and forage for food: their diet consists primarily of insects and other invertebrates, and occasionally small skinks and geckos. They live in the crevices of tree bark, but will frequently wander into homes and vehicles. They are able to travel extremely quickly, often using a springing jump while running, and walk on walls and even on ceilings. They also tend to exhibit a "cling" reflex if picked up, making them difficult to shake off and much more likely to bite. The females are fierce defenders of their egg sacs and young. They will generally make a threat display if provoked, and if the warning is ignored they may attack and bite. The egg sacs differ fairly widely among the various genera. For example, in Heteropoda spp. egg sacs are carried underneath the female's body, while in other species like Palystes and Pseudomicrommata spp., females generally attach egg sacs to vegetation.[17]
^ abGeoffrey K. Isbister & David Hirst (2003). "A prospective study of definite bites by spiders of the family Sparassidae (huntsmen spiders) with identification to species level". Toxicon. 42 (2): 163–171. doi:10.1016/S0041-0101(03)00129-6. PMID12906887.
^Rovner, Jerome S. (1980). "Vibration in Heteropoda venatoria (Sparassidae): A Third Method of Sound Production in Spiders". The Journal of Arachnology. 8 (2): 193–200. JSTOR3705191.
