The apparent increase in spiders during autumn is not due to a greater number of individuals, but rather their increased size and visibility, according to Dave Clarke, an ectotherm specialist at the Zoological Society of London. Spiders hatch in spring and grow throughout the summer, reaching their largest size in autumn, making their webs also larger and more noticeable.
Another reason for their increased presence, particularly indoors, is their search for a mate. Dr Sara Goodacre, a professor of evolutionary biology and genetics at the University of Nottingham, notes that the large spiders seen in homes are typically male teenagers seeking females to continue their life cycle.
Among the species commonly encountered in the UK during autumn are the house spider, cardinal spider, cellar spider, and garden spider. The cardinal spider is the largest native UK species, with adult individuals potentially reaching a leg span of 14cm.
False widows, including the noble false widow, can bite, though confirmed cases in humans are rare. The reaction to a bite is generally similar to a nettle or wasp sting, and they are not considered aggressive.