Spiders

Black Widow

Origin: Five species of these native spiders occur in North America, being found in all states and in southern Canada. Other species may be found worldwide. 

Biology: The black widow spiders are the most dangerous spiders with respect to human health in the U.S. They are one of the few spiders capable of biting humans that inject a neurotoxin, and the effect of the bite can be serious and potentially fatal. Only females bite humans, but both males and females construct webs to capture other prey, primarily flying insects. Males also enter a female’s web for mating, and if the female is not receptive the male may be eaten. The life span of black widow females averages around 180 days as an adult, taking about 3 months to reach maturity. Males mature in about 70 days and live only about 30 days after that. The female may produce up to 9 egg sacs with about 350 eggs per sac on average. She will be most aggressive and defensive of her webbing while she is guarding these eggs, as well as being more hungry following egg production. The new spiderlings emerge from the sac and remain near it for a day or two, but then they undergo “ballooning” to disperse, creating long silk strands that are carried away by the wind. Black widows are generally reclusive spiders that create their webs in areas of inactivity. The web is made of extremely strong silk that is very sticky, and it has a very haphazard appearance without the symmetry of some other spiders. 

Identification: Females are the most recognized spider in North America, with their shiny black body, long thin legs, large oval abdomen, and red “hourglass” pattern on the underside of the abdomen. This hourglass pattern may not always be there. Males also have the same pattern, but it is white, and their body color is mottled brown and white. Immature spiders begin very light colored and progress to the adult color in stages as they pass through their instars, gradually becoming more black if they are females. The female tends to hang upside down in her web due to the weight of the abdomen. Eggs sacs of black widows are about ½ inch in diameter and are smooth surfaced. The eyes of comb-footed spiders are typically a total of eight eyes arranged in two rows of four eyes, one row above the other and with the outside eyes so close together that they touch each other. 

Black Widow

Wolf Spider

Origin: There are over 200 species of wolf spiders found north of Mexico, and these often are the most common spiders in cold climates of high mountains or far northern regions. 

Biology: Wolf spiders are hunters, and use their silk only for lining a nest and for covering their eggs. The females create the tough egg sac and then carry it attached to the tip of the abdomen. Once the eggs hatch the mother then cuts a slit in the sac to allow her young to emerge, and they then climb onto her abdomen to be carried around for up to 2 weeks. Some species of wolf spiders may have leg spans of 4 inches or more and they are very mobile, very fast, and very aggressive when threatened. They are capable of biting humans but the venom is not considered dangerous, but their aggressive behavior makes wolf spiders some of the most feared by people. Smaller species may even “run” across the water of a swimming pool, suspended on the surface tension of the water. Retreats for the spiders are holes in the soil, under debris on the ground or within wood piles. They commonly enter structures and can be found running across floors or walls as they search for food. 

Identification: Wolf spiders vary in size from small species with only ½ inch leg spans to large ones whose legs may stretch out 5 inches. In general they are long legged and covered with short hairs, gray to brown to dark brown in color, and with several darker stripes running longitudinally on the cephalothorax. These body region is somewhat pear-shaped, with the front much narrower than the back and with the front, when viewed from the side, sitting higher than the back. However, the eyes are distinctive, with 8 ocelli arranged in the following manner. The “face” area is usually perpendicular, and the hind pair of ocelli sit at the top of the face, a very large pair of ocelli sit facing directly forward, and 4 smaller ocelli are in an arc below this enlarged pair. 


Wolf Spider