Utah has 18 different bat species, but you'll find only three in urban areas.  These are the Little Brown Bat, the Big Brown Bat, and the Mexican Free-tailed Bat.  All these bats eat only insects such as mosquitoes, beetles and moths which they catch in flight.  One bat can catch from 500 to 1,000 mosquitoes each night.  Bats are one of our most beneficial creatures alive.

As of mid-August 1993, confirmed specimens of the aggressive house spider had been submitted from Cache, Wastach, and Sanpete counties.  These collection sites seem to indicate a general distribution throughout northern Utah.

Strangely, no specimens of aggressive house spider have been submitted from the most populous counties of Utah, although necrotic spider bites have been reported from such counties.  Recent awareness of the aggressive house spider may confirm it's presence in these areas.

The aggressive house spider is a member of the funnel-web spider family. Agelenidae.  Funnel-web spiders are long-legged, swift running spiders that build funnel or tube-shaped retreats.  The aggressive house spider runs at an average speed of about 0.45 meters (17 inches) per second, with a maximum speed of about 1.1 meters (40 inches) per second. 

The aggressive house spider has a brown cephalothorax (the front portion to which the legs are attached) and brown legs, with darker markings on the cephalothorax. The abdomen has a distinctive pattern of yellowish marking on a grayish background, although this pattern can be difficult to discern without the aid of a microscope or hand lens.

Aggressive house spiders prefer to utilize habitats that have holes, cracks, or recesses to support their funnel-like webs.  Although they prefer to build funnel-like webs, some will occasionally produce flat webs in less suitable habitats.  Aggressive house spiders are poor climbers and are rarely seen above ground level.  Although some have been observed a few inches above floor level, most are seen running about on the floor.

Common habitats outdoors include rock retaining walls, cracks in soil or concrete, around foundations (especially those with tall grass adjacent), in window wells, in stacks of lumber, firewood, bricks, or other materials or items, and under other objects on the ground surface, such as large rocks, boards, or other debris. 

Indoors, the aggressive house spider is usually found only in basement or ground-floor levels of dwellings, since it is a poor climber.  Suitable nesting areas include spaces between boxes or other items in storage, window sills, under baseboard heaters or radiators, behind furniture, and in closets.  Wandering males may occasionally becomes trapped in clothing, bedding, shoes, children's toys, bathtubs, or other locations they cannot escape from.

Aggressive house spiders are most commonly encountered in June through September when males wander in search of females.  For this reason, most bites occur during July through September.  Females of the species ten to stay in their webs and are not usually found running about.

The aggressive house spider may be aptly named, since there is some evidence that is more aggressive than other spiders.  Some of this aggressiveness is reflected in its ability to drive other spiders out of suitable habitat.  Also, a few bite cases have been reported where an aggressive house spider has approached and bitten a subject (person or animal) with apparent deliberate intent or has been difficult to dislodge after biting.  Such behavior is not typical of most spiders and has been observed in only a small percentage of aggressive house spider individuals, usually males.

 Five species of widow spiders occur in North America. However, the single species occurring in Washington is the western black widow Latrodoctus hesperus. The adult female is a velvety jet black, but males and immatures are striped with white or yellow.  The underside of the abdomen of the adult female usually shows two reddish markings, often joined to resemble the shape of an hourglass.  The back of the abdomen is usually entirely black, but may be marked with a broken stripe of white, red, or yellow spots.

An adult female including legs, is 3-4 centimeters (about 1 1/2 inches) in diameter.  This species is usually associated with dry, undisturbed piles of firewood, old lumber, dry crawl spaces outbuildings, rock piles, or bales of hay.  Poorly constructed wooden pit privies are favored haunts for these spiders  Widow webs are poorly defined, amorphous sheetings of very strong, fine silk.

The bite of the adult female is more toxic than that of juveniles or males.  However, widows are shy, retiring spiders and bit only reluctantly, usually only when molested.

Widows are more aggressive when they are protecting an egg sac.  The bite of the widow spider causes little immediate pain and my go unnoticed.  Slight local swelling and reddening at the bite site are early signs, followed by intense muscular pain, rigidity of the abdomen and legs, and difficulty in breathing and nausea.  There is little first aid advised other then cleaning the bite and calming the victim.  A physician should be consulted as soon as possible.  Pain can be relieved with injections of calcium gluconate.  In untreated cases symptoms generally fade in 2-3 days.  Widow bites are more dangerous if the victim is a small child or an elderly person.

 This common name refers only to spiders in the genus  Loxosceles. Several species of Loxosceles occur in the United States, but only the brown recluse spider, L. reclusa, and another brown spider, L. laeta, introduced into California and Massachusetts from its normal range in western South American, are known to be dangerous.

The brown recluse spider is common in the southern states, but is sometimes introduced into other areas as a transient on objects or in motor vehicles.  However, the brown recluse does not occur in the Pacific Northwest was found in Prosser in 1978.  This spider came from  a trailer of household  goods brought into the area from Kansas.  No additional specimens have been collected.

These spiders are also known as fiddle backed or violin spiders as they have a dark violin pattern on the front portion of the body.  They have only three pair of eyes instead of four like most spiders.  Their overall size is 2-3 centimeters (3/4- 1 1/4 inches) in diameter. Brown recluse spiders vary in color from tan to dark brown.  They readily enter human dwellings and hide during the daytime in baseboards or ceiling cracks, behind or in furniture, or in undisturbed piles of clothing. 

The bite of the brown recluse spider either may go unnoticed with no after effects or may be followed by a severe localized reaction characterized by scabbing, sloughing off of affected tissues (tissue necrosis), and very slow healing.  Again, as with other suspected spider bites, a physician should be consulted if pain and other discomfort follow the bite.

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