Black widow spiders are most recognized for the red hourglass shape under their abdomen. Contrary to legend, female black widow spiders rarely devour the male black widow spider after mating.
Black widow spiders spin their webs near ground level. They often build their webs in protected areas, such as in boxes and in firewood.
Black widow spiders are often found around wood piles and gain entry into a structure when firewood is carried into a building. They are also found under eaves, in boxes, and other areas where they are undisturbed.
The venom of a black widow spider is a neurotoxin and is used as a defense. Black widow spiders do not bite humans instinctively. The black widow spider bite can cause severe pain. Young children and the elderly are especially susceptible to a severe reaction to a black widow spider bite.
Avoid black widow spider bites by wearing heavy gloves when moving items that have been stored for a long period of time. Spiders often hide in shoes, so check shoes and shake them out before wearing. When spider webs are visible, use caution before putting your hands or feet in that area.
The brown recluse spider, Loxosceles reclusa, is a well-known member of the family Sicariidae (formerly placed in a family “Loxoscelidae”).
It is usually between 6–20 mm, but may grow larger. It is brown and sometimes an almost deep yellow color and usually has markings on the dorsal side of its cephalothorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler or violin spider. Coloring varies from light tan to brown and the violin marking may not be visible.
Recluse spiders build irregular webs that frequently include a shelter consisting of disorderly threads. These spiders frequently build their webs in woodpiles, sheds, closets, beds, garages, plenum, cellars and other places that are dry and generally undisturbed. They seem to favor cardboards when dwelling in human residences, possibly because it mimics the rotting tree bark which they inhabit naturally. They also tend to be found in shoes, inside dressers, in bed sheets of infrequently used beds, in stacks of clothes, behind baseboards, behind pictures and near furnaces. The common source of human-recluse contact is during the cleaning of these spaces, when their isolated spaces are suddenly disturbed and the spider feels threatened. Unlike most web weavers, they leave these webs at night to hunt. Males will move around more when hunting, while the female spiders tend to remain nearer to their webs.
Spiderlings hatch from eggs which are laid from May to July. Eggs are laid in a case of white silken sac. There are approximately 50 eggs in each egg sac. From the egg that is produced from the brown recluse female the spiderlings emerge in 1 month. It takes one year before a spiderling can be considered an adult. It takes a spider about eleven months to reach the adult stage from the time of hatching. Adult brown recluse spiders often live about one to two years. Each female produces several egg sacs over a period of two to three months.
The brown recluse spider is resistant to long periods without food. It can tolerate up to 6 months of extreme drought and scarcity of food.
The venom from a brown recluse spider is extremely venomous. Because of its venom the brown recluse spider is perhaps considered one of the most medically important groups of spiders. Envenomations can result in dermonecrosis and sometimes general systemic illness that can be life threatening; especially for the elderly and children.
To avoid brown recluse spiders, avoid keeping clothing on the floor. Store clothing and shoes inside plastic containers, and shake out all clothing that has been in a hamper before wearing or washing.
The spider species Herpyllus ecclesiasticus is commonly called the eastern parson spider, after the abdominal markings resembling an old-style cravat worn by clergy in the 18th century. It is mainly found in Central USA, with finds stretching from North Carolina to southern Alberta, Canada.
Although this spider presents a startling appearance, living indoors as it frequently does, it is completely harmless to humans or their pets.
The parson spider is a nuisance in homes and is generally non-toxic; although some people may experience allergic reactions to the bites. The parson spider is about 1/2 inch long and may vary in color from brown to black. The front segment of the body tends to be a chestnut color, while the abdomen is grayish with a distinctive white or pink pattern along its middle. The body is covered with fine hairs, giving a velvety appearance.
The parson spider is usually found outdoors under rocks or in piles of brush or firewood. This spider does not spin a web, but wanders on the ground in search of prey. Indoors, this spider wanders about at night and conceals itself beneath objects or in clothing during the day.
Most bites from this spider occur at night or when it is trapped in clothing. While the parson spider is not considered venomous, bite symptoms are variable in severity. Some people may experience localized allergic swelling and itching in addition to initial pain. A few persons may experience excessive swelling, nervousness, nausea, sweating and elevated temperatures from the bites.
Preventing ground spiders and other hunting spiders starts with eliminating their food. Since these spiders eat insects that crawl, inspect the outside for insect entryways. Ground-level entrances should be closed. Check exterior doors to be sure they close properly. Replace any missing weather-stripping. Check basement windows and crawlspace vents for proper screens. Squares of plastic screen can prevent insects from using weep holes as entrances to the home.