Two of the most common poisonous spiders include the Brown Recluse and the Black Widow. Elimination and prevention measures are much the same for all spiders but we have chosen to discuss these as they tend to worry people and are commonly mistaken for other types of spiders.
The Brown Recluse:
These spiders have a light brown body and long legs; the fiddle or violin mark on the region behind the head helps to identify them. Several wolf spiders exist that have a similar shape on the back, and have similar long legs.
Brown recluse spiders occur outdoors, but are most common in large numbers indoors. They can be carried into houses on clothes, in boxes, and in other household material. They tend to gather in undisturbed areas in outbuildings (barns, sheds), and in large storage containers and around garbage cans close to houses. The brown recluse builds an unstructured web, so they are easily overlooked when inspecting for them.
There are few signs of a brown recluse spider infestation. This spideris reclusive and typically does not move far from its web. The bite of a recluse spider is painful, and the site turns red and begins to swell almost immediately. The toxin from this spider remains around the bite and damages the cells in that region. Treatment by a physician should be immediate to avoid long-term scars.
The Black Widow:
Black widow spiders have long legs and a round, shiny black body. On the underside of the adult female there is an orange mark that may look like an hourglass. These spiders are very distinct, and their shape and color markings distinguish them from others that may be inside or outside houses. The black widow spider web is small and has an irregular shape.
Black widow spiders live outdoors. They can be found in their webs on the ground in secluded locations. When around houses, they often gather around the base of a wood pile or along the foundation wall near downspouts. These spiders are usually not numerous, and there may be only one or two in a large area. They are not common indoors, but will move into attached garages and sheds close to houses.
There are few signs of the presence of black widows indoors. They are reclusive spiders and not aggressive. They typically remain in undisturbed areas and are not active during the day. Household infestations rarely carry more than one of two of these spiders.