It seems that there are spider webs all over my yard as well as in the Santa Clarita area where my children live. What kind of spiders are they? I have read about brown spiders that can be dangerous and wonder if I should spray although I don’t want to kill bees and beneficial insects.
What to do?
Joan Gibson, Van Nuys
Spiders are good for the garden, on a par with beneficial insects. While spiders will not overcome, by themselves, an outbreak of a particular insect pest, they will assist beneficial insects in controlling the pest by trapping it in their webs, or by hunting or ambushing it. Similarly, just as beneficial insects, such as praying mantids, for example, will sometimes kill other beneficial insects, spiders too may occasionally trap or ambush a beneficial or even a honeybee. Still, on balance, spiders, like beneficial insects, do far more good than harm. Keep in mind that spiders have eight legs, as opposed to the six legs found on insects, and are an entirely separate animal group, whose members includes scorpions, mites, and ticks.
Spiders are harmless to plants, pets, and people, except on very rare occasions. Depending on which government or university study you happen to find, there are between four and seven people in the United States, on average, who die from spider bites each year. Based on this statistical evidence, the sight of spiders in the garden is no cause for alarm, especially since it is not necessarily the bite, per say, which is the problem, but the infection which follows. Incidentally, around 50 people in the US die each year from the sting of a bee or a wasp, which is nearly always a consequence of an allergic reaction and not due to sting toxicity per se.
You mention brown spiders, sometimes called brown recluse or violin spiders because the pattern on their back resembles a fiddle. Keep in mind, though, that some completely non-toxic spiders have a fiddle on their backs, as well. Although the brown recluse is the most toxic North American spider, only a handful of deaths as a result of its bite have ever been recorded in this country.
Furthermore, according to UC Riverside entomologist (insect expert) Rick Vetters, “there are no brown recluse spiders living in California.” The only brown recluses to have been positively identified here were shipped in moving vans, for example, from other parts of the country, such as the Midwest, which are the actual habitat of these spiders. However, brown recluses have yet to make California their home.
What about black widows, the second most poisonous spider in America, those with the red-orange hourglass emblazoned on their abdomens? Well, as recently as 2013, nearly 2,000 black widow bites were recorded by the American Association of Poison Control Centers. Yet only fourteen of these cases included serious symptoms and none of them led to death.
With such facts in hand, people still fear spiders. When children are asked to identify their major fear, most mention fear of spiders or arachniphobia. Although some of this fear is conditioned by parents whose alarm at seeing spiders is passed along to their kids, there may well be a genetic component to this fear as well, embedded in our DNA.
Based on paleontological findings, it is surmised that the first human beings lived in Africa, where lethal spiders are common. Those who developed a healthy fear of spiders lived longer and had more children than those who lacked this fear. There is also a gender component to arachniphobia since it is evidenced less in men than in women, and is even present more in female babies, according to one study, than in male ones. Since pre-historic hunters were generally men, they would have had to put aside fear of all sorts of wild creatures, many of them more fierce than spiders. This lack of fear, the theory goes, is inheritable.
So even though fear of spiders, going back to the beginnings of the human race, is a sign of a healthy desire for self-preservation, it makes no sense in this part of the world in the 21st century.
You are right, by the way, to be concerned about insect sprays, even organic formulations, since they are highly toxic to spiders.
As much as earthworms are evidence of fertile, well-aerated soil, spiders are a sign of ongoing pest control in the garden. Spiders provide an around-the-clock security service that assists in the control of leaf hoppers, leaf miners, aphids, caterpillars, thrips, horseflies and ants. A spider eats two times its weight in insects every day.
All spiders produce silk, but not all spin webs. Spiders are divided into two groups: Orb weavers and hunters. Orb — referencing the circular web that they construct — weavers are the most noticeable garden spiders because of their large size, enormous webs and the bright, symmetrical patterns on their abdomens. Webs are used not only for catching insects. Spiders, if not completely blind, have poor vision and use their webs as a means of communication. This is especially true in mating, since a courting male must vibrate a female’s web in just the right way to distinguish himself from a trapped insect. Incidentally, although black widow females occasionally consume their male partners after mating, this is not typically the case.
Hunters, such as the ubiquitous, hairy-legged and famously cannabalistic wolf spiders, are webless creatures that capture their prey by ambushing or jumping on them.
Aside from webs, spiders use their silk for making nests, protecting their eggs and binding up insect prey. Combfooted spiders live in the lower branches of trees and in the corners of our rooms, from which they keep a watch out for insect intruders. Crab spiders can immobilize themselves on a flower for a day or more waiting for an unsuspecting insect to land there and then pounce.
Spiders are the only animals whose food is digested outside their bodies. This is accomplished by depositing digestive enzymes into their prey, which liquefies their tissues prior to consumption.
Spiders feed not only on insects, but on other spider species, as well as on their own kind. In a University of Kentucky study, when predators of the common wolf spider were removed from a soybean field, wolf spider mortality was still high, the result of cannibalism.
Tip of the Week: There are several ways of attracting spiders to the garden. Aside from mulch, which provides the ideal nesting ground for spiders that hunt their prey, cover crops such as clover or vetch, as well as hedges and windbreaks are welcome havens for spiders.
In a study at the University of Nebraska, crops near windbreaks had more spiders, lady beetles and parasitic wasps and fewer insect pests as compared to crops not sheltered by windbreaks. Tall flowers such as sunflowers also provide a welcoming haven for spiders, as do vining beans and the vertical stalks of sweet corn.The point of growing a diversity of plants around your vegetable garden is to keep the beneficial insects and spiders there after a crop is harvested.