Spiders in House
Estimates spiders inside a typical house by room count.
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Spiders in your home
A 2016 NC State study (Bertone et al.) counted ~30-100 spiders in the average home, and most of them go unnoticed by the people living there. Brazil has roughly 3,500 species, but only three groups matter medically: the armadeira or banana spider (Phoneutria), the aranha-marrom or brown recluse (Loxosceles) and the viúva-negra (Latrodectus). Almost everything else is a harmless predator that feeds on cockroaches, mosquitoes and flies.
Numbers peak in autumn (Mar-May), the season when males roam looking for mates. Antivenoms come from Instituto Butantan (SP) and Vital Brazil (RJ); in 2024 the SUS distributed about 50.000 doses for arachnidism cases across the country.
Applications
Household pest management, public health work (Butantan, Vital Brazil), Anvisa control under RDC 52/2009, and the environmental Lei 9.605/1998, which protects predators.
FAQ
Are spiders dangerous? About 99% of the ones in homes are harmless. Try to identify before killing, since most are working in your favor.
What to do if bitten? If you can do it safely, photograph the spider. Wash the wound and head to a hospital that stocks antivenom.
How to reduce population? Cut off their food by dealing with other insects, seal up cracks, and clear out cluttered storage spots.
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