As we reach the middle of summer, spider populations are peaking. Though most spiders are venomous to some degree, very few of them pose any real threat to humans. That being said, people seem to have an almost instinctual aversion to spiders, probably a lingering evolutionary response that helped early humans to survive. As with all personality traits, there are varying degrees of fear associated with spiders, and those with the greatest fears are classified as phobic. Rather than focusing on the rarely encountered venomous species of spiders found in central Pennsylvania, we will take a look at some of the most common spiders we find in and around our local households.
This is the Common house Spider, known internationally as the American House Spider. They make their random entangled webs primarily in and around structures, most commonly found around eaves and near windows, where the daylight will attract flying insects. Adults of this species can live for more than a year, and a female will produce as many as 17 egg sacs in her lifetime, each containing as many as 400 eggs. These spiders will hide or flee when a large disturbance is detected in their web, and will only bite humans under extreme conditions, such as being grabbed and squeezed. The female venom is a neurotoxin similar to that of the black widow, but far less powerful, and may or may not result in itching and swelling at the bite location, depending on the amount of venom injected.
This spider is commonly known as the Cellar Spider, though some refer to them as Daddy Long Legs. This reference can be confusing though, because many people refer to an unrelated species of arachnid called a Harvestman as a Daddy Long Leg. The Harvestman is not actually a spider at all.
Cellar spiders hang inverted on their tangled, random webs, and prefer to build in cool, damp areas such as caves and basements, though they are often also found in drier environments such as attics. When they perceive a threat, they will vibrate their bodies in a gyrating motion, making it hard for a predator to focus on them. For this reason, they are sometimes referred to as vibrating spiders. This spider is very frail and fragile, and poses no real risk to humans.
This is the Yellow Sac Spider. They are usually pale in color ranging from yellow to beige, though I’ve heard them described as “white” spiders. This spider or abandoned web is most commonly encountered where the wall meets the ceiling inside homes. Yellow sac spiders build a web around themselves almost like a cocoon. As with most species of spider, they will only bite humans in extreme circumstances, and will prefer to flee from a larger threat rather than attack. A bite from a yellow sac spider contains venom that may cause a small lesion on humans. Some species of yellow sac spiders are attracted to the volatiles in gasoline, a phenomenon that led to the recall of 65,000 Mazda autos in 2009 and 2010 when it was discovered that yellow sac spiders were building nests in the fuel systems.
The term Jumping Spider refers to a wide variety if spiders that have the ability to jump several times the length of their bodies, both when attacking prey, or as a defensive movement. Jumping spiders have incredible vision in many different directions. Unlike other spider species, the jumping spider does not rely on a web to catch prey; they are hunters, not trappers. They will pounce on their prey and rapidly inject their venom, followed by immediate consumption. While most times they will not use a web for hunting, jumping spiders do produce silks that they will use as a tether or safety net when jumping. Some species also build silken tents to sleep in and to protect themselves from weather and predators. Their egg cases are also stored in these tents.
The Domestic House Spider is also referred to as a Funnel Weaver, because of the shape of their webs. They build elaborate funnel shaped webs in windows and corners. I also sometimes see tremendous numbers of these spiders in shrubbery and landscaping. They hide out in the funnel and wait for prey to become entangled, at which time they attack with surprising speed and agility, dragging the prey back into the funnel where they feed. This species does not store food like many species do. This spider rarely injects venom when inflicting a defensive bite (dry bite) as it prefers to store and save it’s venom for intended prey. If the venom is injected into humans, it can cause a small lesion similar to a burn. In healthy adults, this venom will have little to no effect, and medical attention is normally not needed.
When encountering spiders in and around your home, remember that no spider will aggressively or even randomly bite a human. Use common sense, and do not put the spider into a situation where it has no choice but to bite defensively. If you would rather not see spiders in your home, a quarterly pest control program will do an excellent job eliminating spiders from your home and surroundings.
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