Spiders

There are 3,000 species of spiders living in North America and over 35,000 known worldwide. Spiders are not insects, but are arthropods of the class Arachnida.

Identifying a Spider

Spiders have two body regions, the head and the abdomen. This arthropod lacks antennae and has four pairs of slender legs. Male spiders are generally smaller than the females, though the exact sizes vary depending on the species. For example, an American house spider is about 3/16” long, while a female tarantula is about 3”.

An adult female Black Widow is about 1/2” in length and has a spherical black abdomen with 2 reddish marks on its underside, resembling two triangles forming an hourglass.

An adult brown recluse has a 1/2 inch long body and its color can range from tan to dark brown. This spider is also called a fiddleback, due to its distinctive fiddle-shaped markings.

The Damage Spiders Can Cause

Most spiders will not bite unless provoked by handling or other contact. In many cases, bites occur when a person inadvertently comes in contact with a wandering male spider or a spider habit (such as in a seldom used attic or basement). Many spider species cannot pierce human skin with their fangs, and those that can generally leave the area in a state of minor irritation and swelling.

Of the groups present in the United States, only two have been identified as a serious dangerous for humans: the black widow and the brown recluse. The female black widow’s bite delivers a neurotoxin to the victim’s system. Symptoms include high body temperature and blood pressure, profuse sweating, and severe nausea. Immediate medical attention is required.

The brown recluse’s venomous bite can be delivered by either male or female members of the group. The bite is often not felt immediately, but does produce intense pain which can be delayed for as many as 6-8 hours. Symptoms of the bite include restlessness, fever, and difficulty sleeping. However, the most severe danger of this bite is the tissue damage itself. The spider’s venom kills the surrounding tissue which eventually sloughs off leaving an open ulcer and possible exposing muscle or bone. Immediate medical attention is required.

Spiders’ Life Cycle

After mating, a female spider will deposit eggs in a silken sac. Depending on the species, one sac can carry 20 eggs or several hundred. In general, those species that tend their eggs will produce fewer per egg sac, while those that abandon the sacs will produce larger numbers.

It is extremely rare for a female spider, including the black widow, to eat the male after mating.

Many spiders live only 1-2 seasons, but some species can live for as long as 20 years.

Spiders’ Habits

Most spiders are nocturnal and shy of human activity.

All spiders are predators and the primary food source is insects and other arthropods. After capturing their prey, the spider will kill or paralyze it with venom. When food is scarce, a spider can survive several weeks or months depending on the species.

Of the black widow spiders, only the females deliver a venomous bite (adult males do not carry venom and spiderlings are only poisonous when ingested). The female is only aggressive when defending her eggs and is generally only active at night.

The brown recluse, as the name implies, is shy of activity and can be found in undisturbed areas such as boxes, closets, and attics. The brown recluse will generally prefer to escape rather than attack, but will attack if threatened. Most cases involve people donning seldom worn clothing or shoes, or digging through storage areas.

In many species, the young will demonstrate a habit called ballooning. This involves climbing to a high point, spinning a silk thread and then floating out on the breeze in order to disperse themselves around the area.