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There are numerous species in the family Loxosceles. The genus has a cosmopolitan distribution. L. reclusa (violin spider, brown recluse spider in North America) and L. laeta (South America) are the most familiar and notorious. Other species include L. rufescens (cosmopolitan), L. arizonica, L. deserta, L. rufipes (North America), L. spinulosa, L. parrami (South Africa). They have a body length of 8-15 mm and a leg length of 2-3 cm. They have a beige-brown colour with a dark spot in the form of an upside-down violin dorsally on the cephalothorax (the "violin" points to the rear of the abdomen). There are three pairs of eyes (dyads), one in front and the others on the sides. They share this characteristic with spiders of the family Scytodes ("spitting spiders"). They are more active at night, but can also bite during the day. In nature they can be found under stones, logs, etc., but the animals also often enter houses and thrive in this environment (they are "synanthropic"). They are often found there in large numbers. In South America L. laeta is known as the "araña de los rincones" ["rincón" = corner], which refers to this peridomestic character. In so far as their psychology is understood, spiders only bite when they feel threatened. They live 1 to 3 years.
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The venom of Loxosceles sp. is primarily cytolytic and haemolytic. A bite by Loxosceles reclusa can produce significant skin wounds, with necrosis and tissue loss. Clinically, a bite results in initial pain followed by mild skin irritation. After 6 hours or so the pain intensifies. There are local vasospasms and ischemia develops. An itching oedema with a red halo and purple centre develops. A central bulla can form. This can evolve into a necrotic wound which nevertheless remains limited to the skin. Underlying muscle tissue is not affected. A deep scar can remain. If the bite is on the face, the oedema can cause respiratory problems. Occasionally there are systemic reactions with haemolysis and anaemia, clotting disorders, kidney failure and, in exceptional cases, death. The patient can develop chills and fever, macular rash, joint pain, nausea and vomiting. Leukocytosis, thrombocytopenia, anaemia, icterus, haemoglobinuria and proteinuria can follow. The treatment is essentially symptomatic. Tetanus prophylaxis must not be overlooked. When a patient is seen soon after a bite, dapsone, 50-100 mg twice per day can be given, in order to limit the necrosis. It is best if G6PD-deficiency is excluded first. The efficiency of dapsone is not clear however. In rare cases a dapsone hypersensitivity syndrome can develop. In this case the patient develops fever, headache, nausea and vomiting, lymphadenopathy, hepatitis, haemolysis and reversible leukopenia. The wound should not be debrided too quickly (wait up to 2 weeks). Sometimes a skin graft may be necessary. When kidney failure or clotting disorders occur, the patient should be hospitalised. Steroids probably have little utility. The use of hyperbaric oxygen is experimental. Specific anti-Loxosceles antiserum exists, but is usually not available. In endemic areas skin ulcers are often attributed to these animals without adequate justification. Frequent misdiagnoses include: herpes, ecthyma, insect bites, etc.
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These spiders, also known as black widows, have a cosmopolitan distribution. Other names which are sometimes used for animals from this genus are the katipo (New Zealand), redback spider (Australia), button spider (South Africa), malmignatte (Mediterranean area), karakurt (Southern Russia). There are no black widows in central and northern Eurasia. There are several species and subspecies: Latrodectus mactans mactans, L. mactans hasseltii (Australian black widow), L. m. tridecimguttatus (Europe and South America), etc. Only the female spiders bite. L. mactans measures 20-25 mm and often bears a typical red hourglass-shaped spot on the ventral abdomen. In nature they frequently sit upside down, with the red warning spot clearly visible. Completely black specimens do occur. L. geometricus ("brown widow") varies from yellow-white to jet black. This spider is found in southern Africa and the warm areas of the New World, but it rarely bites. Latrodectus curacaviensis is found in Brazil. The creatures spin a web in protected corners of fields, gardens, near stones and woodpiles and in vegetation. They are rarely found indoors. L. variolus prefers to live in trees. Upon superficial inspection, the animals can be confused with Steatoda paykulliana (Europe) and Steatoda grossa (USA): false black widows. Only bites by female black widows are potentially dangerous. Unlike loxoscelism, neurotoxicity plays a central role with latrodectism. The direct local reactions at the bite site are often minor or insignificant. The venom contains alpha-latrodectin, a neurotoxin that triggers an increased release of neurotransmitter at the nerve endings. This results in a presynaptic depletion of the vesicles. Acetylcholine, noradrenaline, dopamine, glutamate and enkephalin systems are all sensitive to the toxin. The venom induces painful muscle spasms, abdominal pain and hypertension. The clinical symptoms are muscle rigidity, primarily abdominal ("pseudo-appendicitis"), fasciculations, general weakness, sweating, excessive salivation, vomiting, fever, hypertension and possible ptosis, photophobia and priapism. Often an acute abdomen will be included in the differential diagnosis. If the neurotoxicity is pronounced, weakness of the respiratory muscles can develop with respiratory arrest. Children have a higher risk of a fatal outcome. Sometimes facial oedema can develop (Latrodectus facies). For treatment, benzodiazepines are used against the muscle spasms and painkillers to reduce the abdominal pain. Calcium gluconate infusions have little effect. Hypertension which does not improve after pain control sometimes requires nitroprusside or nifedipine. Antiserum can be given in serious cases, but is rarely available. The potential benefits of the antiserum must be weighed against the disadvantages (anaphylaxis, serum sickness). In serious cases the antivenom should be given without hesitation (an initial allergy-test probably has little value). The patient will start to improve after 30'.
In Australia there are 35 species of funnel-web spiders. They have a funnel-shaped web, often with triplines to detect their prey. Atrax species are large, aggressive spiders. The most notorious is the Australian Atrax robustus or Sydney funnel-web spider. This spider is found within a 160 km radius of Sydney. The venom of the spider includes a neurotoxin with potentially fatal consequences for humans. The animals have a glistening black cephalothorax and a velvety black abdomen, sometimes with some reddish hairs. The fangs can be up to 5 mm long and can penetrate a fingernail. The spider makes its web under stones, logs, hedges, near vegetation and fences. Clusters of up to 150 animals have been found. With Atrax robustus the female always stays near her web, while the males roam about. Thus the latter can come into houses. With this species, the bite of the male spider is much more serious than that of a female spider and is justifiably highly feared. The venom includes the small protein robustoxin, a unique presynaptic neurotoxin. The venom interferes with the release of the neurotransmitters noradrenaline and acetylcholine at the level of the motor and autonomous nerves. A bite by Atrax is followed by intense pain. This is probably due to the mechanical damage and the acidic pH (4.5) of the venom. No dermal necrosis results. In serious cases there follows a rapidly progressive neuromotor syndrome which can be fatal within two hours. Initially there is local piloerection and muscle fasciculation. These symptoms become generalised with tingling sensations around the mouth and tongue and lip spasms. Within a half hour they are followed by marked hypertension, tachycardia, 2nd degree AV block, hyperthermia, haemoconcentration and coma with increased intracranial pressure. Copious sweating, excessive salivation, lacrimation, diarrhoea and muscle cramps follow. The excretion of catecholamines in the urine shows a peak after two hours. Asphyxia can lead to death (occurs only with bites by male spiders). If the patient survives, there follows hypotension and intermittent apnoea after one or two hours, possibly with pulmonary oedema. This too can be fatal. Muscle enzymes (CK) can rise substantially. Children are at higher risk than adults. Shortly after a bite it is recommended that a splint and a lymphatic tourniquet ("pressure immobilisation technique") should be applied. In this way the systemic resorption of the venom is slowed down and the patient can be transferred to a hospital. Antitoxin has been available in Australia since 1981. The antitoxin is prepared in rabbits, starting from Atrax venom and Freund´s adjuvant. As a guide dose 200 mg IV of purified IgG (= 2 ampoules) is administered. This can be repeated every quarter of an hour, until there is improvement. The antitoxin is probably also protective against other Atrax species. The role of antihistamines is unclear. Oxygen, mechanical respiration with PEEP, atropine (against bronchorrhea and excessive salivation) and short-acting antihypertensives should be used depending on the symptoms. Since acute stomach dilatation can develop, nasogastric aspiration must be performed.
Hadronyche formidabilis (earlier Atrax formidabilis or "northern funnel-web spider") is found in the central coastal region in New South Wales and the nearby Blue Mountains. The animal prefers to live in trees such as Melaleuca, Banksia and Eucalyptus, at a height of several metres. Hadronyche cerberea also lives in trees. While Atrax robustus is limited to southeast Australia, Hadronyche sp. are also found in east Tasmania.
Trechona venosa is a large South American funnel-web spider which lives in caves or on plants near the Atlantic coast. The animal is black or grey-brown with yellow stripes on the abdomen. An adult animal has a body length of 30-45 mm (7 cm with legs). A bite can be accompanied by intense pain.
Banana spiders are ctenid spiders who belong to the genus Phoneutria. These aggressive South American spiders are nocturnal hunters (no web). They often hide in bunches of bananas, hence their popular name. P. nigriventer measures 35 mm in body length. The body is often brownish grey with a white stripe on the dorsal abdomen. Females have a black abdomen while males are more orange. The spiders typically have fine reddish brown hairs around the base of the chelicerae. Phoneutria keyserlingi is found in the Brazilian state of Sao Paulo. P. columniana is found in Colombia and P. boliviensis is found from Costa Rica to Bolivia. Phoneutria fera is unusually aggressive and tends to bite several times at the same site in quick repetition. The venom is a complex mixture with several neurotoxic components. It acts on both the peripheral and the central nervous system. A bite is followed by sharp pain, and then by tachycardia, hypertension, hypothermia, profuse sweating, excessive salivation, nausea and vomiting, priapism and dizziness. Death can occur within 6 hours and is generally attributable to respiratory arrest. A polyvalent antiserum (anti-Loxosceles and anti-Phoneutria) is produced by the Butantan Institute in Brazil. Both local infiltration and IV administration of the antitoxin are performed. Due to the danger of respiratory suppression, it is best to avoid opiates.
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Wolf spiders belong to the Lycosidae family. They are nocturnal hunters which generally do not spin webs. Earlier it was believed that they hunted in groups, hence the popular name. Some species of this group care for their offspring. They carry the cocoon containing the eggs along with them, and the young, once they have emerged, remain for some time on the back of their mother. Wolf spiders include species with a moderately cytotoxic venom. The best known is the European tarantula (Lycosa tarantula). However, the name tarantula is used for several different animals and hence gives rise to confusion. Its bite was earlier deemed to provoke tarantism in the victim, a syndrome characterised by stupor and a wish to dance…. Possibly this refers to the consequences of Latrodectus bites, rather than Lycosa itself, since the latter only causes local pain, swelling and erythema. It is also possible that the name stems from the Italian town of Taranta. Lycosa raptoria is a South American tarantula species (the venom is also locally cytotoxic). Tetanus vaccination, painkillers and local disinfection suffice for bites by these animals.
"Bird spiders" belong to several genera. Some people keep them as "pets", although several species are protected under the CITES convention (Convention on International Trade in Endangered Species). Theraphosa leblondi and Grammostola mollicoma are large spiders with a body length of 7-10 cm and a leg span to 21-26 cm. They live in tropical and subtropical areas. Several American genera of bird spiders have fine urticarial hairs: Lasiodora, Grammostola, Acanthoscurria, Brachypelma, Avicularia, Hapalopus. The density amounts to 10,000 fine hairs/mm2. When the animals feel threatened they rub with their legs over their back, detaching the fine urticarial hairs which are armed with small barbs. These can be released by the thousands and cause persistent itching when they come into contact with the skin and work their way under the surface. Penetration into the cornea or inhalation can lead to serious consequences. The fine hairs have a typical appearance when examined with a slit lamp. They are somewhat shorter than 2 mm. Four types can be recognised according to their microscopic fine structure. When handling these animals, wear gloves and glasses, avoid rubbing your eyes and wash carefully after manual contact. Bites by these spiders cause local pain and swelling, whether or not followed by lymphangitis. Otherwise the consequences are not serious. The treatment is symptomatic. Beware of the fact that urticating hairs are also present on exuvia (shed skin), even when preserved in alcohol!
Tegenaria agrestis ("hobo spider" or "northwestern brown spider") and Tegenaria campestris are hairy funnel-web spiders (fam. Agelenidae) which can cause necrotic arachnidism. Some Tegenaria species are often found indoor, in the bathtub, where the animal cannot scale the smooth walls. A small necrotic spot with surrounding erythema is typical, but certainly does not always occur. Vesicles can form. Systemic effects include vision impairment, headache, hallucinations, general weakness. They are small creatures of 10-15 mm, atypically brown. Originally from Europe, T. agrestis was accidentally introduced into North America, where the animal now thrives. Little is known about treatment.
The so-called "white tailed spiders" (Lampona sp.) are encountered in large parts of Australia, including urban environments. They are easily recognised by their cylindrical body and the white or grey spot at the end of the abdomen. They are active hunters. A bite from such a spider can give rise to local redness and vesicle formation. Sometimes ulceration can follow (rather exceptionally). There is no specific antiserum. Hyperbaric oxygen therapy has been used, but its utility is disputed.
Chiracanthium (id. Cheiracanthium) species are found around the globe. They are notorious for their annoyingly painful bites. A bite is followed within 30 minutes by local itching and redness. Sometimes this can evolve to local necrosis. Systemic effects include (rather rare) nausea and abdominal pain, as well as headache. In North America C. inclusum and C. mildei are well known. The latter was accidentally introduced into the USA. C. diversum was unintentionally taken from Australia to Hawaii. In South Africa C. lawrencei is responsible for numerous nocturnal bites. The treatment is symptomatic.
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