The worldwide estimate of described spider species is over 46,000. Out of those, only about 200 species have been demonstrated to be of medical concern to humans. There are over 3,800 spider species in North America. Just to let you breathe easier, you’ll be happy to know the majority of them live outdoors, away from our homes. Experts say about 30 species are known to be synanthropic (lives in association with humans). Now, isn’t that a relief!
You are probably wondering with all these spiders around, are they a threat to my family and me? In North America, only the widow spiders and recluse spiders are of medical concern. Almost all spiders have venom, so the potential is there for some people to have a reaction to a bite. One interesting fact is, spiders are able to control the amount of venom released, so some bites could have little to no venom injected.
The fangs on many spider species are too short to readily pierce the skin. The spider must be pressed against the skin to allow penetration. If a bite does occur, it’s important to collect the spider or the remains for positive identification by a competent person. Some physicians do not have sufficient training to identify spider species, so it’s best to have an entomologist, arachnologist or pest management professional identify the spider. No one, not even a doctor or veterinarian, can identify a so-called bite wound from a spider or insect unless it has been collected or seen while actually biting the victim or found nearby at the time of the bite.
Many sores, blisters, or necrotic lesions that are diagnosed as a spider bite without any evidence of the spider, are most likely due to some other condition…Such as Staphylococcus infection and Sporotrichosis, both of which have been misdiagnosed as spider bites.
There are four native species of widow spiders found in North America… The Southern Black Widow, Northern Black Widow, Western Black Widow, and the Red Widow. The Brown Widow is an introduced species. The red or reddish hourglass on the underside of the abdomen is a key identification characteristic. The egg sac from the Brown Widow has small soft spikes or orbs on its surface, while native widow eggs sacs are smooth-surfaced in comparison.
There are six native species of recluse spiders found in North America, with the Brown Recluse spider having the largest range. There are also two introduced species found occasionally. The Mediterranean Recluse and the Chilean Recluse. Key identification characteristics would be the often-apparent fiddle shape mark on the cephalothorax and the three pairs of eyes. Most other spiders have four pairs of eyes.
Here are some facts about spider bites in general:
Many believe spider bites are quite common, which simply is not true
Spiders have no interest in us as a food source
They feed on insects and other invertebrates, not on human blood
The truth is spider bites are quite rare, that’s the reality of it
There are many insects that do sting, bite, and feed upon us. We have mosquitoes, fleas, ticks, and bed bugs, just to name a few. These known blood feeders have the potential to cause a reaction from our bodies that may be, and often are, misdiagnosed as a spider bite.
So, what can be done to keep spider populations down? Inside clutter such as boxes, paper, clothing, etc., should be discouraged. Outside debris such as lumber piles, firewood, stones or bricks, landscape timbers, etc., should be moved away from the home. Grass should be cut at the recommended height and shrubs should not come in contact with the home or other structures on the property.
Now, go get busy cleaning up for spring, and don’t get overly excited when seeing a spider or two… They are not your enemy!