Spiders

The Black Widow spiders get their common name from the popular belief that the female eats the male after mating, a phenomenon which rarely happens in nature.

Adult female body length about 1/2" long.  Their color is typically black, abdomen with 2 reddish triangular markings usually joined to form a reddish hourglass-shaped marking.  Adult males usually consists of a median row of red spots with white lines or bars radiating out to sides.

Young spiders primarily orange and white but acquire more and more black as they mature, with markings very similar to those of males.  With 1 or 2 reddish markings on underneath side of abdomen.

Female black widow spiders deposit their eggs in silken egg sacs.  When constructed these egg sacs are white but will turn pale brown.  The maximum number of sacs per female ranges from 6 - 21 and the average eggs per sac is about 185 - 464.  The sacs outer covering is tough and closely woven.

Most of the spiders overwinter as immature individuals, developing into adults in the spring, and die in late July, taking nearly a year to grow from egg to adult.

These spiders spin an irregular web and hang from it in an inverted or upside down position.  The web is used to ensnare prey.  The female avoids light in sheltered places, and tends to work her web at night.

In terms of poison bites only the female is of concern.  Her venom is a neurotoxin.  She is normally shy and retiring, but aggressively attacks immediately after egg laying and when guarding her eggs.  The only reliable evidence is of a bite is a slight swelling with 2 tiny red spots where the fangs entered.  There is an antitoxin available.  Immediately call a physician or go to an emergency room if bitten and take spider along for identification purposes.

The Brown Recluse or Fiddle Back spider gets its common names from its coloration and reclusive habits, or the dark violin/fiddle back-shaped marking on the top of the cephalothoraxes. 

Adults are usually about 1/4-1/2" in body length.  Color is tan to dark brown with a darker fiddle-shaped marking on dorsum.  They have 6 eyes arranged in 3 groups of 2.

The female deposits 40-50 eggs in a silken egg sac which is off-white.  From 1-5 sacs are produced.

The female spins an irregular web in undisturbed areas.  The web is not used to ensnare prey, but mostly as a retreat for the spider.

Both males and females inject venom, and must be considered dangerous to humans.  Injection of the venom should be treated by a physician or at an emergency room immediately.  If possible take the spider along for identification purposes.

Inside the home, they can be found in almost any undisturbed area to which they can gain access.  They are most commonly found in boxes, among papers, and in seldom used clothing and shoes, although they can be found in corners, underneath tables and chairs, or in crevices such as those found along baseboards, doors, and window moldings.  They typically run for cover when disturbed.

The common name Cellar spider comes from these spiders frequently found in the dark and damp places such as cellars, basements and crawl spaces, and that of daddy longlegs from the very long, thin legs.  Cellar spiders are a nuisance pest, probably more because of its web then the spider itself.

Adult body length ranges from 1/16 - 5/16".  They have a very tiny waist but appearing as a small body with very long, thin legs.  They are usually pale yellowish to light brown or gray.  Normally with 8 eyes,  2 widely spaced groups of 3 and 2 eyes in between.

The long bodied female may produce up to 3 egg sacs each containing 13-60 eggs each.  The sacs are very thin and a cluster of eggs usually show through.  The female will normally carry the egg sac between her jaws until they hatch.

Cellar spiders construct loose, irregular webs in corners.  They hang upside down on the underside of the web.  They constantly install new webs.  This habit can result in extensive webbing in a  relatively short time.  Webs are commonly found in damp dark places such as cellars, basements, and crawl spaces.  They can also be found in the corners of garages, sheds, barns, and warehouses, on eves, windows, warehouses, these spiders tend to be in corners near doors which are left open.

Cellar spiders seem to fare better in areas with high relative humidity.  When disturbed on its web, the long legged cellar spider has the habit of rapidly shaking its body in a rotary movement.  This causes the web to vibrate enough to blur both spider and web, making the spider seem to disappear.

The common name Hobo spider comes from this spider's method of vary rapidly expanding its distribution by hitching rides with humans along major highways in the Pacific Northwest; it was formerly known as the aggressive house spider.  Their webs are a nuisance but their bite is of medical importance to both humans and pets because it may result in a slow-healing lesion.

Adult female body length is about 7/16 - 5/8" long.  Male body length is 5/16" -7/16".  Color varies from light to medium brown, with dark stripe to either side of lighter midstripe. and 5 light colored triangular shaped loops on each side bordered by a dark background .

The bite from these spiders typically produces a necrotic lesion similar to that caused by brown recluse spiders.  The fully developed lesion may be up to 1/2-1" or more in diameter.  It may take several months to heal and often leaves a permanent scar.  Treatment is similar to that of a brown recluse spider.  Antibiotics do nothing to alleviate the effects of the venom.

Hobo spiders may be found in almost any habitat containing holes, cracks, or crevices which support tunnel formation.  Since they are poor climbers, they are rarely found above ground level.  They frequent dark, moist areas, and are often found in basements, window wells, and crawl spaces.

These spiders build funnel webs opening at both ends with one end expanding outward into a broad, slightly curved sheet.  An escape tunnel is commonly built in the back of the web which leads to a deep crack or other protected area.

The common name House spider or Domestic spider reflects the fact that this is usually the spider most often encountered indoors.  It is a nuisance pests, probably more because of its webs than the spider itself. 

Adult female body length is about 3/16 - 5/16".  Male body length is 1/8 - 3/ 16".  Color is yellowish brown, abdomen is dirty white with a few dark spots to almost black, with several dark stripes.  Legs are orange in males, but yellow in females.

Female house spiders lay about 250 eggs in a silken sac which is brownish.  There may be more then one sac at a time.

The house spider randomly selects its web sites.  If a web does not yield prey it is abandoned, and another site is selected, and a new web built.  Because the web site is selected by trial and error, many webs may be constructed in several days.  Dust collecting on these webs accentuates their presence.

Inside structures, house spiders are most likely to be found in upper corners, under furniture, in closets, angles of window frames, basements, garages, and crawl space.

The common name Wolf spider reflects that these are hunting spiders and will chase their prey.  These spiders are often big and hairy which alarms some people, but they are primarily a nuisance pests.

Adult female are  3/8 - 1 3/8".  Adult males are  1/4 - 3/4".  Their color is usually dark brown, often with paler stripes or markings, or sometimes yellow with dark stripes or markings.

The egg sac consists of an upper and lower half united at the middle.  It is carried on the female and is usually white, sometimes green, but changes to dirty brown  or dirty gray with age.  It may contain between 100-365 eggs depending on the species of wolf spider.

Wolf spiders actively hunt during the night and sometimes during the day.  They are fast on the feet and pursue prey.

Some wolf spiders build retreats consisting of either a shallow excavation under a stone, or a tube running vertically into the ground.  They leave their burrows primarily at night to hunt insect prey in the surrounding area.  They do not build snare webs.

These spiders may enter structures in search of prey.  Although they are not inclined to be permanent residents in structures, once inside, they often stay.  They often tend to stay at or near floor level, especially along walls under furniture and other objects.  Wolf spiders may be brought in with firewood.

(Insect Information excerpted from the NPCA Field Guide to Structural Pests)