If there's one thing we have no shortage of in California, it's spiders. We have dozens of species of spiders. Luckily, most of them are harmless and in fact beneficial because they eat pest insects like mosquito.
Spiders, of course, are not insects. They're arachnids. The two most obvious visible differences between spiders and insects is that adult spiders have eight legs instead of six, spiders have their head and their thorax fused together into one part called the cephalothorax, and spiders never have antennae.
Although most spiders are harmless, most people would rather they not live inside their homes. Many spiders can bite, and although most spider bites are harmless, they can be annoying. But there are three species of spiders common in California that actually are dangerous to humans, and which should always be controlled if they're found in or around homes or other human occupied areas. These three species are black widow spiders, yellow sac spiders, and wolf spiders.
Black Widow Spiders
The Western black widow (Latrodectus hesperus), sometimes called the Western widow, is the most notorious and easily-recognizable of California's dangerous spiders. Female black widows have black bodies that are about half an inch in length, black legs, and and usually have a red, roughly hourglass-shaped marking on their lower abdomens.
Male widow spiders are much smaller than females and are usually tan in color. They produce very little venom, and their bites are usually harmless. Contrary to popular belief, females of Latrodectus hesperus usually do not consume their males as part of the mating ritual. Only a few "widow" spider species do, actually, and ours isn't one of them.
Female Western widow spiders do, however, produce a very toxic venom. The latrotoxins that is contains are potent enough to sometimes cause death in humans, especially children, the elderly, and the infirm. All suspected black widow bites should be treated as medical emergencies.
Most widow bites, however, are not fatal. But they are extremely painful and can cause spasms, muscle rigidity, vomiting, sweating, and temporary paralysis, and there's no reliable way to predict whether a person will recover without medical care; so it's important to seek medical care any time a person is known or suspected of having been bitten by a black widow.
Yellow Sac Spiders
Yellow sac spiders range in size from one-quarter to one-half inch. They're usually yellow to yellowish-white white in color, and the legs and cephalothorax are usually darker in color than the abdomen.
Two species of yellow sac spiders are found in California: Cheiracanthium mildei (shown here), which is the one more commonly encountered as a household pest; and Cheiracanthium inclusum, which is usually found outside and is of less concern as a pest.
Cheiracanthium mildei is the yellow sac spider that's usually found in homes. They often build resting sacs (sort of like hammocks) in high corners or behind furniture that's against the walls, and emerge at night in search of insects. They prefer resting in high places, but if they are disturbed they usually slide down to the floor on a silken thread.
Yellow sac spiders are timid and non-aggressive, but they are capable of inflicting painful bites if, for example, one is hiding in your shoe when you put it on. They produce a necrotizing venom that causes cells around the bite to die, much as the brown recluse does.
That's why those of us on the West Coast consider sac spiders to be our version of brown recluse spiders. But yellow sac spider bites usually heal in about two weeks (unlike brown recluse bites, which can take months to heal) and rarely cause complications other than local redness, swelling, and blistering.
Wolf spiders are stocky, robust, solitary spiders that are usually tan with brown or black markings. They can grow to an inch or more in length. Most of the wolf spiders in California belong to genus Pardosa, which contains several species that are very similar and very difficult to tell apart.
None of the wolf spider species commonly found in California make webs. Instead, they hide or lie in wait in places where prey insects are likely to pass by, and pounce on them when they do. They're excellent hunters and are equipped with two large, forward-facing eyes (out of eight total eyes) that provide excellent forward vision for hunting. The eyes are quite prominent and are also a quick way to identify wolf spiders.
Another unique identifying feature of wolf spiders is that females carry their egg sacs under their abdomens until they hatch, at which time the spiderlings climb onto their mothers' backs. Adult females can often be seen either with their abdomens elevated carrying their egg sags around, or with their young riding on their backs.
Wolf spiders can deliver a painful bite that can produce localized redness and swelling, but generally does not cause serious complications unless the individual is allergic or sensitive to the bites.
Bust-A-Bug provides spider control in Brentwood, Contra Costa County, and all of our Bay Area service area. The methods used vary with the species and the situation, but may include trapping, exclusion (sealing them out), or insecticide treatments (especially exterior treatments to help prevent them from getting into the house in the first place). Please contact us for more information about spider removal or any of our quality pest control services.