By Whitney Cranshaw, Colorado State University Cooperative Extension, Entomology
The banded garden spider (Argiope trifasciata)is the most common "garden spider" found in the western US. They produce large, conspicuous webs amongst shrubbery and other large vegetation in late summer. The webs of the garden spiders are very concentric and resemble those of the most famous garden spider of all- Charlotte's Web.
The banded garden spider spends the winter either as eggs in a large silken sack or, primarily, as tiny "spiderlings" hidden in protected areas of the garden. These very young spiders get around primarily by "ballooning", carried by breezes that catch silken threads the spiders produce. Upon settling on an appropriate site, they begin to produce their characteristic webs between sticks, grass, or other upright vegetation.
Flying insects that become caught in the webbing are quickly paralyzed by the bite of the spider and are wrapped in a sheet of webbing. After feeding, the spiders usually cut the dead insects out of the web and allow them to drop to the ground. While tending the web, the female typically remains in the center both day and night, repairing it when it gets torn.
The spiders grow throughout the summer, reaching full-size in late August and September. The males, which are much smaller than the females and do not produce webs, roam around the vegetation and mate the females in late summer. The female then lays one or more egg sacks, that appear somewhat like a small kettle drum with a tough papery cover and may contain 1000 eggs apiece. The spiders die after frost and there is only one generation produced each year.
Other Common Late Summer Spiders: Another very large orb-weaver is Araneus gemma. This is sometimes called the "cat-face", "monkey-face" or "humpback" spider since it has a pattern of dark markings and raised areas on its back that seem face-like. Females of this spider are generally rounded with angular 'shoulders' and can reach a size exceeding a quarter. They make webs in undisturbed corners, often near porch lights, and are often found in late August and September around the eaves of houses. Unlike the banded garden spider, A. gemma hides in dark corners at the edge of the web during the day. She remains in contact with the web via a "trap-line" thread that signals when insects have been ensnared.
Probably the most common spiders found in homes during late summer are the grass spiders, also known as the funnel-web spiders (primarily species of Agelenopsis). They are generally brown, typically with light and dark bands running along the back. They make dense webs in grass or amongst shrubbery that have a central hole where the spiders rest awaiting a passing insect to contact the web. When temperatures drop they very commonly migrate to the warmth of buildings that they temporarily invade.
Photo: Leon Higley, Dept. of Entomology, University of Nebraska
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010