The answer to this question depends greatly on climate and the species of spider in question. Spiders reproduce year round in tropical regions. North American spiders can breed in the spring, summer, or fall, or all three seasons. Typically, spiders in the U.S. and Canada appear more abundant in autumn because most of the large orb weavers reach adulthood at that time, and as the foliage falls from trees their webs become ever more obvious. Further, fall is mating time for many of the hunting spiders like tarantulas, trapdoor spiders, wolf spiders, and others; and the males will frequently enter homes and other buildings looking for mates, even those species normally confined to webs. Female orb weavers north of Mexico generally produce egg sacs in the fall and some species overwinter in that condition. Look for wolf spider females to be toting egg sacs from their spinnerets, often in spring or summer.