Residential, Structural and Community Pest Logo
NCSU logo - click for NCSU home page

Spiders In and Around Homes
By: Michael Waldvogel and Charles Apperson, Extension Entomology
Insect Note - ENT/rsc-1

wolf spiderSpiders have a well-established but largely undeserved reputation as being dangerous to the health of people and their pets. In truth, spiders are extremely beneficial because they prey on many insects that we consider to be true pests in our homes and gardens. Not all spiders build elaborate webs to catch their prey. Some species ambush their prey from tubular tunnels built in the ground, under rocks or other areas. Other species simply build a loose collection of webbing in which they live. These types of spiders, such as the wolf spider shown here, are the ones that most frequently invade homes. They may remain hidden for most of the day, then hunt for prey at night.

Biology of spiders

Spiders are not insects. They are close relatives of ticks, mites and scorpions, which all belong in the group called arachnids. Unlike insects, which have three main body sections and six legs, spiders have two body sections and eight legs. The eyes, mouthparts and legs are found on the front section of the body, known as the cephalothorax. The second section, the abdomen, bears the parts of the respiratory system (spiracles and/or book lungs depending on the type of spider), the digestive and reproductive systems, and the external organs used for spinning silk or webbing. Most spiders are identified by size, color, markings on the body and the number (usually six or eight) and arrangement of eyes. Female spiders wrap their eggs in a silken spun sac. Some spiders carry this egg sac, while others deposit it somewhere within their nest. Hatchling spiders (spiderlings) often produce a silk thread that allows them to disperse by "ballooning", i.e., being blown by wind currents to other areas.

How dangerous are spiders?

Encounters between people and spiders are usually accidental and bites are a response by the spider when its web or nest is disturbed. Most spiders produce venom therefore, they could be considered "poisonous". The venom is stored in glands that empty into the spider's fangs or chelicerae. For the most part, spider bites are insignificant. However, just as bee and wasp stings may trigger allergic reactions in some people, the same can be true for spider bites. Young children, the elderly and hypersensitive individuals are more likely to react more strongly to a spider bite. In North Carolina, there are few spiders that can inflect serious and painful injury. The two best-known poisonous spiders found here are the black widow spider and the brown recluse.

Control of Spiders Outdoors

Spiders are beneficial and control many insects that feed on the flowers, shrubs and other plants in our gardens and natural areas. Spraying for spiders in these areas may actually increase the number of pests by killing off other natural enemies as well. Web-building spiders are most likely to show up in areas where insects are abundant, e.g., wood piles, around porch lights, windows or water sources (such as water spigots). Knocking down these webs with a broom or burst of water from a garden hose is adequate for "control". Outdoor pesticide applications for spiders are largely unnecessary and should be avoided. On occasion, you will find spiders on objects or in areas that have been left undisturbed; this can include sandboxes or even children's toys. Check these items periodically for signs of spiders. Spraying pesticides around sandboxes or other play areas should be avoided whenever possible.

Finding a large number of spiders indoors usually means that there is an ample supply of insects and other "spider food" in the area. Any real attempts to get rid of spiders should focus on eliminating these insects. The long term solution includes non-chemical measures:

  • Sanitation - reducing or eliminating conditions that attract insects, e.g., high moisture and ready access to food of some sort.
  • Exclusion -find the entry points used by both insects and spiders and seal or close these areas.

There are a number of short-term solutions to spider infestations, as well. Knocking down and removing webbing, or mechanically removing/killing the spiders should be sufficient. Vacuum the areas along baseboards, in corners and under and behind furniture. Clean bookshelves periodically. If you're concerned that more spiders will show up (or hatch from an unseen egg sac), then you could resort to applying an insecticide along baseboards, in corners, and inside storage closets. Select a pesticide that is labeled for use against spiders indoors. Always read the insecticide label for complete instructions on how and where to use the product. Crawlspace are often attractive environments for spiders (but not necessarily the source of spiders entering your living area). Treating your crawlspace is an option, but simply setting off foggers ("bug bombs") is not likely to be effective and can be hazardous particularly if you contaminate your heating/AC ventilation system. Crawlspace treatments, if needed, are often best left to pest control professionals. The availability of particular insecticides may change from year to year, so consult the latest edition of the NC Agricultural Chemicals Manual or your local county Cooperative Extension office for advice on selecting insecticides.

Tips on Avoiding Spider Bites

Follow these suggestions to reduce the chances of being bitten:

  1. Always check for spiders before sticking your bare hand(s) into dark corners or areas where you can't see your fingertips.
  2. Always wear work gloves when handling boxes, firewood, lumber and other items that have been left in storage undisturbed for signficant periods of time.
  3. Vigously shake clothing and shoes that have been left undisturbed for some time to dislodge any spiders and inspect them before wearing.
  4. If you think you have been bitten by either a black widow spider or brown recluse, carefully apply ice or a cold-pack to the bite and seek medical assistance. If you can catch the suspect spider, bring it along for positive identification or take it to your local county Cooperative Extension office for identification.

For additional information about spiders in your garden in your garden, read Common Spiders in the Landscape. Additional informational about spiders and spider myths is available at the Burke Museum Website

Lycosid spider image courtesy of Dept. of Entomology, University of Nebraska-Lincoln

References used in preparing this publication:
Goddard, J. 1993. Physicians Guide to Arthropods of Medical Importance. CRC Press, Boca Raton, FL.
Kaston, B. J. 1953. How to Know the Spiders. Wm. C. Brown Co., Dubuque, IA.

Pest information and control recommendations presented here were developed for North Carolina and may not be appropriate for other states or regions. Any recommendations for the use of chemicals are included solely as a convenience to the reader and do not imply that insecticides are necessarily the sole or most appropriate method of control. Any mention of brand names or listing of commercial products or services in the publication does not imply endorsements by North Carolina Cooperative Extension nor discrimination against similar products or services. All recommendations for pesticide use were legal at the time of publication, but the status of pesticide registrations and use patterns are subject to change by actions of state and federal regulatory agencies. Individuals who use chemicals are responsible for using these products according to the regulations in their state and to the guidelines on the product label. Before applying any chemical, always obtain current information about its use and read the product label carefully. For assistance, contact the Cooperative Extension Center in your county.

Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Updated 2008
linked map area for Notes home page linked map area for Entomology Department home page linked map area for NC Cooperative Extension Home page