Spiders. The Black Widow Spider (Latrodectus spp.)The black widow spider (Latrodectus spp.) is a spider notorious for its neurotoxic venom. It is a large widow spider found throughout the world and commonly associated with urban habitats or agricultural areas. Although the common name ‘black widow spider’ is most commonly used to refer to the three North American species best known for their dark coloration and red hourglass pattern, it is occasionally also applied to several other members of the Latrodectus (widow spider) genus in which there are 31 recognized species including the Australian red-back, brown widow spider (sometimes called the gray widow), and the red widow spider.
In South Africa, widow spiders are also known as the button spiders. Currently, there are three recognized species of black widow found in North America: The southern black widow (L. mactans), the northern black widow (L. variolus), and the western black widow (L. hesperus).

Southern Black Widow (L. mactans)

The southern black widow, L. mactans , is found in Pennsylvania. It is probable that the northern black widow, L. variolus , is also present. Occasionally, the brown and the red widow spiders are introduced on potted plants from southern Florida. The female southern black widow is normally a shiny, jet-black spider 8 to 13 millimeters in body length. With legs extended, the female measures about 25 to 35 millimeters long. The male, which is black and has white underbody markings with red spots, is only 4 to 6 millimeters long (12 to 18 millimeters including its legs). The female has the well-known reddish hourglass marking on the underside of her abdomen. The bite of female black widows is, at first, relatively painless. Pain will be felt about one to two hours later, and occasionally the patient may experience a tingling along the nerve routes or down the spine. There is almost no swelling at the site of the bite. However, the site will typically exhibit two red fang marks and may be surrounded by a rash or erythema. Black widow venom is principally neurotoxic. Generalized body symptoms, which develop within one to three hours, may include any of the following: nausea, chills, slight fever, rise in blood pressure, retention of urine, burning sensation of the skin, fatigue, motor disturbances, breathing difficulty, constipation, and muscle aches, particularly in the abdomen. These symptoms usually disappear after four days. Death does not normally occur, except in the elderly or very young. Treatment typically includes the use of calcium gluconate (to reduce muscle cramps), Latrodectus antivenom, and diphenhydramine hypochloride to counteract allergic reactions to the antivenom. Additional treatments include antispasmatic medications and analgesics.

Northern Black Widow (L. variolus)

With the days and nights getting cooler there isnt much time left to be in the field. This is my favorite time of year to look for Latrodectus variolus. These are more elusive than L mactans mostly because of its habitat. While L mactans seems to prefer more open areas that are rocky and even close to human dwellings, L variolus prefers heavily forested areas which are located on ridges and hillsides. Juveniles and males have nice colors. This is an adult male. Finding the webs can be difficult, however if you walk with the Sun in front of you they will glow when sunlight hits them. The webs are typical of other Latrodectus in that they are tangled and the silk is very strong. L variolus seems to prefer to make their webs among the leaf litter on the ground. Often they make their retreat next to a small bush, in this case a Wild Huckleberry.

Western Black Widow (L. hesperus)

Outdoors, western black widow spiders may be terrestrial or live above the ground. Indoors, they build their webs in undisturbed areas that are not frequented by humans. In arid parts of Arizona, this spider inhabits almost every crevice in the soil and its nests are found in cholla cacti and agave plants. The western black widow female’s body is about half an inch long. Females have a complete hourglass marking on the underside of the abdomen, which is usually completely black except for a small reddish spot near the tip. As female western black widows grow older, they gradually develop into a shiny black or dark brown, with a bright red or orange hourglass. The male is less than half the size of the female. Males of the western black widow have three diagonal pale stripes on each side of the abdomen and are usually light brown, whereas males of the other species of Latrodectus are generally black. Mature male western black widows do not drastically change their body coloration and resemble juveniles of both sexes. Yet, like the female, the male’s hourglass becomes brighter in color, usually yellow or orange.