Distribution

Worldwide, from tropical to temperate zones. Main area of distribution of the potentially dangerous Scolopendridae in tropical zones.

Biology

Elongated, dorsoventrally oblate body, which, as with all arthropods, is surrounded by a chitinous external skeleton. Body uniformly segmented. There is a pair of legs on each segment, in contrast to millipedes (Diplopoda), which have two pairs of legs on each segment and have a more or less rounded body profile. A pair of antennae is located on the head, as well as eyes, although these may be absent, and mouth parts. The venom claws (maxillipeds) that extend along the underside of the head arise from the first segment behind the head.

  Fig. 4.90 Scolopendra sp.

Around 3,000 species are known and are subdivided into 4 orders: Scutigeromorpha, Lithobiomorpha, Geophilomorpha and Scolopendromorpha. The Scolopendridae, a family belonging to the latter order, include the only species that can lead to significant envenoming in humans, not least because of the enormous size of some members of this family. Scolopendra subspinipes and S. viridicornis, commonly found in the tropics, reach a length of up to 18 or 19 cm, and Scolopendra gigantea even up to 25 cm.

Chilopods are predominantly nocturnal animals, and are photophobic. They live in the soil substrate, under leaves, loose tree bark and the like. If exposed to daylight they try to escape into dark crevices. As predatory animals they use their venom apparatus primarily to overpower their prey, but if seriously threatened they will also use it in defence.

Risk

All chilopods possess venom claws, but even if these are able to penetrate human skin, in most cases bites are no more than painful. Due to the reclusive nature of these animals, bites in humans appear to be relatively uncommon. A retrospective study of records from the National Ministry of Health of Venezuela reported only 12 cases of scolopendra bites in the 30 years between 1966 and 1996, all of them involving adult victims (cited in: Rodriguez-Acosta et al. 2000).

In the older literature there are occasional reports of fatalities following Scolopendra sp. bites, but the accuracy of most of these reports has been questioned (Bücherl 1971c). Nonetheless, reports of systemic envenoming caused by larger Scolopendra species must be taken seriously.

Laypersons often confuse millipedes (Diplopoda) with chilopods (see above for the distinction). Millipedes posses venom glands that open out along the sides of the body but are not associated with an injection apparatus. Some species in New Guinea can spray venom. If the alkaloid-containing secretions enter the victim's eyes, this leads to a severe burning sensation. On the skin, the secretions of most species only cause a temporary discolouration. Some tropical species cause skin rashes and blisters (Burtt 1947, Haneveld 1958, Keegan 1963, Radford 1975).

First aid

Diplopods: Washing the skin and washing out the eyes with water in order to remove secretions.

Diagnosis

Diplopods: Examination of the eye, including fluorescent staining, in order to exclude injury to the cornea.

Treatment

Diplopods: Symptomatic, in particular prevention and treatment of secondary infections. Treatment of corneal ulcers with atropine and local antibiotics.

Literature (biological)

Keegan 1963, Bücherl 1971c, Minelli 1978, Jangi 1984, Rodriguez-Acosta et al. 2000