With a few exceptions, mygalomorph spiders were generally considered less dangerous than their bad reputation implied. However, there are increasing reports of envenoming caused by bites from these spiders that can result in local and even generalised muscle cramps.

Bird spiders are generally larger, sturdy species whose largest members reach a body length of up to 11 or 12 cm. Consequently the venomous fangs are often large and solid. Thus they can inflict powerful bites that may be accompanied by secondary infections. Apart from local effects of the venom, some species may also cause generalised muscle cramps. Bird spiders are popular pets, and it is not rare for their owners to be bitten. Small children are generally more sensitive to the venom than adults.

Below is a list of members of this group that have caused accidents in humans or that are considered potentially dangerous. Bettini and Brignoli (1978) provide a more detailed summary.

Ctenizidae: Falltürspinnen, Trapdoor spider. Found throughout the world. The species mentioned here are now included in the family Actinopodidae. Actinopus sp. causes local pain, as do the Australian Missulena sp. Missulena bradleyi was held responsible for a case of systemic envenoming in a 19-month-old child (Sutherland 1990).

Dipluridae: Funnel-web spiders. Found primarily in the southern hemisphere. The most notorious genera from this family, Atrax spp. and Hadronyche spp., are nowadays classified under the family Hexathelidae. According to Bücherl (1971b) bites from several species of the South American genus Trechona could be fatal for humans.

Theraphosidae: Bird spiders, "Tarantulas" (American name). Found throughout the world, with the greatest variety of species in South America. Accidents in the wild are rare, as on the one hand most species that inflict defensive bites are very shy and on the other their habitats rarely overlap with the areas in which humans live. If Bird spiders are kept in terraria, it is probable that defensive bites will occur far more often because of the frequent handling. Two bites from the South African species Harpactirella lightfooti were marked by local pain, vomiting and signs of shock (Finlayson and Smithers 1939).

Fig. 4.43 Pterinochilus sp. Typical appearance of a Bird spider.

The venom of the east African Pterinochilus sp. shows marked neurological effects in mice. In contrast, according to Freyvogel et al. (1968), bites in humans generally take a trivial course. However, one publication from the year 2009 (Ahmet et al.) refers to a case of generalised muscle cramps following a Pterinochilus murinus bite. In the same publication, generalised muscle cramps following a Lampropelma nigerrimum bite are described, and the authors refer to various reports from laypersons of the occurrence of muscle cramps in particular following bites by Eumenophorus sp., Selenocosmia sp. and Stromatopelma sp. People who keep Bird spiders as pets should therefore handle African, Asian and Australasian animals with caution.

In the USA Anophonopelma bites only lead to local effects. Many New World members of the family Theraphosidae (Ischnocolinae, Grammostolinae, Theraphosinae and Aviculariinae) possess so-called urticating hairs on their abdomen that they can use defensively by kicking or rather firing them off their abdomen with their rear legs. If these hairs come into contact with the eyes or mucous membranes in humans, they can cause inflammatory reactions (Bücherl 1971b, Cooke et al. 1972, 1973).

Literature (biological)

Bettini and Brignoli 1978, Smith 1990

Classification according to The World Spider Catalogue.

The Tarantula Bibliography