Spiders
Wolf Spiders (Fun Fact): They do not spin webs, and they also prefer living and hunting alone.
Non-venomous to humans. Bites may cause rare allergic reactions. The most common species you will encounter is the Carolina wolf spider. Can grow up to about the size of a silver dollar (1.5 inches). Outside the house, they frequent tall grasses and garden patches as well as exterior walls. Inside they prefer dark, isolated spaces where they can hide when not hunting for food. This means homeowners often discover them in attic corners, basements, and around baseboards.
Grass Spiders (Fun Fact): They are often mistaken for wolf spiders, but the size and pattern of eyes can most easily distinguish them.
Also known as funnel weavers. Unlike their Australian counterpart, all grass spider species in Colorado are non-venomous to humans. They are generally brownish or grayish spiders with a body length the size of tic tac to a small paper clip (0.30 to 0.70 inch). They capture prey with a horizontal sheet web. In one corner of the web is a narrow funnel “retreat". The web is not sticky but usually includes vertical strands that can help impede passing insects.
Jumping Spiders (Fun Fact) The jumping spider family alone contains 13% of all spider species.
Non-venomous to humans. These spiders vary in color and behavior. Typically, black with a white line that runs on the upper part of the abdomen with two white dots close to the rear. A little longer than a grain of rice (0.27 to 0.35 inch). The average spider can jump up to 2 feet.
Cellar Spiders (Fun Fact): Have been known to vibrate the webs of other spiders to draw in an easy meal.
Non-venomous to humans. 34 species of cellar spider live in North America. Head and abdomen are different shades of a dull brown. Less than a 1/2-inch body, 2-inch-long legs, and the body is the shape of a peanut.
European Garden Spider (Fun Fact): The first web they build will always be the perfect one. Each time they have to build a new web, imperfections show.
Non-venomous to humans. True to its name, this species lives primarily in gardens and similar habitats. It builds its web in the midst of shrubbery, flowers, and small plants. Comes in a variety of color patterns such as white, yellow, and brown. Active near dusk. Can be the size of a quarter dollar in length (0.90 inch).
Yellow Sac Spider (Fun Fact): They are nocturnal, so they do build small “sac” webs or nests during the day, in which to rest.
Considered mildly venomous to humans. Most bites on humans occur when people are gardening or performing other kinds of outdoor activities. Are light yellow to pale yellowish green, sometimes with an orange-brown stripe on top of the abdomen. These spiders are active hunters who do not wait in a web for prey to come to them, but rather go out in search of food. Typically, the length of a sewing pin (1 inch).
Western Black Widow (Fun Fact): Widow spiders rarely, if ever, bite when not within a web. Bites may be more likely if the female is tending an egg sac in the web, which she will defend.
Considered venomous to humans. The distinguishing feature is the presence of a red or reddish orange “hourglass” pattern on the underside of the abdomen. However, this pattern can be highly variable with the western widow. Females are typically black whilst males are dark brown. They usually reach a length of a coat button (0.25 to 0.35 inch).