Spiders

While spiders may evoke fear or dislike in many individuals, it's important to recognize their significant role as predators of insects and other arthropods, making them beneficial creatures. The majority of spiders pose no harm to humans. Spiders that have the potential to cause harm, such as black widows, typically prefer to remain hidden under furniture, boxes, or in secluded areas like woodpiles, corners, or crevices. Spiders that are commonly observed in open spaces during the day are generally not inclined to bite humans.

In general, spiders do not seek to bite humans unless they feel threatened or provoked, such as being squeezed or unintentionally disturbed. Additionally, the size of their jaws is often too small to penetrate adult human skin. Occasionally, if a spider is disturbed in its web, it may instinctively bite, mistaking the disturbance for trapped prey.

The effects of a spider bite can vary depending on factors such as the species of spider, the amount of venom injected, and the age and health of the individual bitten. A spider bite may cause no reaction at all, or it could lead to mild symptoms such as itching, redness, stiffness, swelling, and pain, usually comparable to a bee sting. Typically, these symptoms subside within a few minutes to a few hours. However, individual responses to spider bites can differ, so if a spider bite results in an unusual or severe reaction, such as increasing pain or extreme swelling, it is advisable to seek medical assistance from a physician, hospital, or poison control center.

Black Widow

The black widow spider, scientifically known as Latrodectus hesperus, is the most common harmful spider found in California. Its bite can result in a range of reactions, from mild to painful and serious. However, it is highly unlikely to cause death, and many symptoms can be alleviated with proper medical treatment. If someone is bitten by a black widow spider, it is important to stay calm and seek immediate medical advice. It is also helpful to try and capture the spider for identification purposes.

Adult female black widow spiders have a shiny black body, slender black legs, and a red or orange hourglass-shaped mark on the underside of their large, round abdomen. The body length, excluding the legs, ranges from 5/16 to 5/8 inch. Only the larger immature females and adult females have the ability to bite through human skin and deliver enough venom to cause a painful reaction.

On the other hand, adult male black widow spiders are approximately half to two-thirds the size of females. They have a smaller abdomen and often go unnoticed. While male black widows do possess venom, their fangs are too small to break through human skin.

Black widow spiders can be found in various regions of California. They typically inhabit dark, dry, and sheltered locations that are relatively undisturbed. These places include piles of wood, debris, or rocks; culverts; hollow stumps; old animal burrows; garages; sheds; barns; crawl spaces; utility meter boxes; outhouses; and sometimes among plants. The risk of being bitten by a black widow spider is highest when individuals inadvertently disturb the spider while cleaning or handling objects in such areas. Taking precautionary measures such as wearing gloves and a long-sleeved shirt is sensible when working in undisturbed areas that offer favorable hiding spots for spiders.

Brown Recluse

There are no established populations of the brown recluse spider, Loxosceles reclusa, in California, and only a small number of verified specimens have been collected over several decades. However, people in California often share stories of supposed brown recluse spider bites or receive diagnoses of brown recluse bites from physicians. It's important to note that there are other species of recluse spiders found in southern areas of California that can cause similar medical concerns. The purpose of this publication is to provide accurate and science-based information regarding the presence of the brown recluse and related spiders in California.

Misdiagnosis of necrotic wounds as "brown recluse bites" has contributed to the widespread awareness of recluse spiders throughout North America. While recluse spiders are capable of causing such wounds, available biological data suggest that many of these diagnoses are incorrect. A renowned toxicology physician who worked at the University of Southern California Medical Center has estimated that the majority of general spider bite cases referred to him in California were actually caused by other arthropods. Furthermore, 60% of "brown recluse spider bite" diagnoses came from areas where Loxosceles spiders were not known to exist. This misdiagnosis poses a serious problem, as several medical conditions mistakenly attributed to recluse bites can lead to severe and potentially fatal consequences.

In the event that you experience a necrotic wound in California, it is important to consider numerous other common causes that are significantly more likely than a bite from a brown recluse spider. If an arthropod is involved, it is crucial to first consider various creatures that specifically target mammals for blood meals and have the potential to cause necrotic-type wounds. Examples of such arthropods include mites, fleas, bed bugs, soft ticks, hard ticks, conenose bugs, and kissing bugs. Consulting with a medical professional is advised for proper evaluation and diagnosis.

Management

It is important to recognize that spiders play a valuable role in the garden as beneficial creatures. In most cases, the use of pesticides to control spiders is challenging and seldom required. Instead, the most effective method for managing spiders in and around the home is to eliminate hiding places for secretive species like black widows and regularly remove spider webs from the house using brushes or vacuums. By taking these measures, you can maintain a balanced environment while minimizing the presence of spiders.

Spiders can find their way into buildings through cracks and openings, or they may hitch a ride on items such as plants, firewood, or boxes. Regularly vacuuming or sweeping windows, room corners, storage areas, basements, and other infrequently used spaces helps to eliminate spiders and their webs. Vacuuming can be an effective method as their delicate bodies typically do not survive the process. An old web covered in dust indoors indicates that it is no longer in use by a spider.

To remove individual spiders from indoor areas, place a jar over them and carefully slide a piece of paper under the jar to seal the opening when lifting it up.

Preventing spiders from entering indoor spaces involves sealing cracks in the foundation, gaps around windows and doors, and ensuring good quality screening that not only keeps out spiders but also the insects they feed on.

In storage areas indoors, elevate boxes off the floor and away from walls whenever possible to discourage spiders from using them as hiding spots. Sealing boxes with tape will prevent spiders from taking up residence inside. It's important to declutter garages, sheds, basements, and other storage areas, and remember to wear gloves to avoid accidental bites.

Outdoors, eliminate hiding places for spiders and their webs by keeping the area around the foundation free from trash, leaf litter, dense vegetation, and other debris. Trim plant growth away from the house and other structures to discourage spiders from establishing residence nearby and venturing indoors. Outdoor lighting attracts insects, which in turn attracts spiders. If feasible, keep lighting fixtures away from structures, windows, and doorways. Regularly sweep, mop, hose, or vacuum webs and spiders off buildings. It's generally not recommended to use insecticides against spiders outdoors as they do not provide long-term control.