Toxicology
The katipo has medically significant venom in humans, although bites are rare. The incidence of bites is low as it is a shy, non-aggressive spider. Their narrow range, diminishing population, and human awareness of where they live means interaction between humans and the spider is minimal. The katipo will only bite as a last resort; if molested, the spider will usually fold up into a ball and drop to the ground or retreat to the nearest cover. If the threat continues, the spider may throw out silk against the interference. When restrained in any way or held against skin, such as if tangled up in clothing, the spider will then bite defensively. However, if the female is with an egg sac it will remain close by it and sometimes move offensively to bite any threat.
Bites from Katipo spiders produce a syndrome known as latrodectism. The venoms of all Latrodectus spiders are thought to contain similar components with the neurotoxin α-latrotoxin the main agent responsible. Most bites are caused by female spiders; the male katipo was considered too small to cause systemic envenoming in humans. However, bites from male redback spiders have been reported suggesting male Latrodectus spiders can cause envenoming in humans. Although bites by male spiders are much rarer than those by females, perhaps due to their smaller jaws rather than lacking venom of similar potency to females or being unable to administer an effective bite. Māori legends recall many deaths, the last of which appears to have been a Māori girl who - according to the missionary Thomas Chapman - died in approximately 1849. While there were reports of severe katipo bites in 19th or early 20th century records, no other fatalities from spider bites have since been reported in New Zealand. The most recently reported katipo bite as of 2012 was to a Canadian tourist in 2010.
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