Brown Recluse Spider
Appearance:
The continental U.S. is home to 6 species of brown spiders belonging to the family Loxoscelidae. These spiders are also referred to as violin spiders and fiddle-back spiders because of a violin-shaped, darker brown pattern on the cephalothorax of these spiders.
The Loxosceles brown spiders are similar in coloration, having a light brown cephalothorax outer margin, light brown or beige abdomen and medium to dark brown legs and violin pattern on the cephalothorax.
The eye pattern is characteristic for this family and constitutes the most reliable method for identification. The six dark eyes are arranged in 3 pairs (3 diads). One diad is located on the front middle portion of the face and the other 2 diads are located on either side. The 3 diads lie along the lower rim of the violin shape.
The brown recluse, Loxosceles reclusa, is the best-known of this family and is most common in the South and Southwest. Adults range 1/4 to 3/8 inch in body length and have a leg span of 1 to 1 1/2 inch. Males are similar in size to females but have slender abdomens. When disturbed, the legs are frequently held in a somewhat crablike posture with the 3 front pairs of legs arching forward and the hind legs arched backward.
Habitat:
Brown recluse spiders actively hunt for small prey through the night and in darkened rooms during the day. Females spin thin silk retreats in undisturbed sites where they spend the daylight hours. Such sites include seldom-used hanging clothing and shoes in closets, the lower folds and plaits of curtains, draperies, and the skirting around sofas, stuffed chairs and beds. Other sites may be among storage (especially cardboard boxes and papers) and clutter in warm attics, basements and garages, also under the edges of carpeting and behind baseboards.
In commercial buildings, heat tunnels and boiler rooms may harbor these spiders. Outdoor harborages are usually not an issue in the Midwest as they are in the South. The female produces 1 to 5 silken egg sacs during their lifetime, each typically containing 30 to 50 eggs (maximum 300). The eggs hatch in 25 to 39 days and the spiderlings undergo 8 instars (growth stages between molts). Development requires about a year. Indoors, females live 2 to 5 years while the male lifespan is under 2 years.
Most cases of bites attributed to these 2 species by the public and by healthcare professionals are false and speculative. Other insect and spider bites (e.g., those of yellow sac spiders and funnelweaver or grass spiders) and/or secondary bacterial infections are more likely responsible for the lesser incidents that have been reported by those involved. It is important for the person who is bitten to seek out and save a specimen of the spider that inflicted the bite for the healthcare professional or consulting entomologist to identify, if possible.
Diet:
Brown Recluse spiders eat any insect they can capture. They paralyze or kill their prey with venom, then inject a fluid that enables them to suck out the digestive liquid food. They can survive without food for several weeks to a few months.
Solutions:
What you can do: The likelihood of introducing dangerous spiders within structures and encountering them in and around buildings can be reduced by:
- Eliminating tall and dense vegetation close to the foundation which serve as harborage for spiders and their prey (e.g., vines, groundcover, juniper, uncut grass and weeds),
- Excluding gaps under doors (by replacing or adding door sweeps), lower courses of siding, around utility penetrations and weep holes in brick veneer,
- Capturing wandering spiders on ground level, in basements and in attached garages by placing sticky traps indoors along walls behind furniture, washer, dryer, sump pump, water heater, furnace, commode, and storage (out of reach of children and pets), and
- Removal using a shop vacuum cleaner or household vacuum fitted with a hose attachment; this is useful for removing spider webs as well,
- Thoroughly inspecting goods and produce trucked in from the South, Southwest and from Mexico on the loading dock or receiving area for stowaway spiders before storage, processing and distribution occur.
Professional Solution:
A Quik-Kill service technician will apply an exterior barrier treatment around the foundation perimeter, beneath lower siding, under eaves and porticos, along exterior molding/trim, thresholds, patio, deck and chimney attachments, as well as inside and around sheds and other outbuildings.
A regular pest management service program may be required in cases where large populations of spiders are present and where landscaping conditions and locality are conducive to their propagation. Indoors, basement sillplates and perimeters, as well as the corners and edges of spider-infested rooms, can be treated.
