Eeek! All about spiders, our eight legged neighbors.
Welcome to Kings Park Focus on Nature.
I have a confession to make. Although I enjoy nature and it’s many diverse forms, I’m not totally comfortable with spiders. We’re not talking about a full-blown case of arachnophobia here. It’s just that I don’t harbor a particularly warm feeling towards these creatures. Ok, if one of them gets the jump on me, maybe I even get a bit of the hibigeebies. Just a little bit. Now that I’ve put that out there, let’s see if we can gain an appreciation for them as I write this blog. Maybe writing about arachnids will help me work through my issues!
To begin with, spiders are not insects. True, like insects, spiders have a jointed exoskeleton, and so belong to the phylum of animals known as arthropods. Whereas insects possess three main body parts, spiders have two. The “head” of the spider is called the cephalothorax. The “back end” of the spider is called the abdomen. The two sections are connected by a piece of anatomy called a “pedicel”. The eight legs are attached to the cephalothorax. The cephalothorax is also the business end of the spider. This is where the chelicerae, aka “fangs”, are located. The other end of the spider is equipped with it’s “spinerets”. These two tools, the fangs, and the ability to make silk, make it an efficient predator. This basic body plan has allowed the spider family to prosper for over 400 million years.
Nearly all spiders are predators, and thus beneficial to us as they help keep pest insect populations in check. Typically, spiders inject their prey with venom, which kills it. Once the victim is immobilized, they use their fangs to inject a digestive enzyme that liquefies its innards, creating an insect “slurpee”, which the spider ingests. Some species process their food by chewing the prey’s internal organs while mixing it with the digestive enzymes. In either case, the food must be taken in as a liquid, which is the only manner in which the arachnids specialized digestive system can take in nutrients. It is true that the venom of some spiders, such as the Black Widow, genus Latrodectus , or the Brown Recluse, Loxosceles reclusa, (not native to our region) can pose a danger to humans. The likelihood of being bitten by one of these creatures is minimal, however. Since most spiders are retiring and shy being bitten by any species is uncommon. The probability of the spider being stepped on by a human is much higher! Rashes often called “spider bites” are more likely caused by other sources, such as allergic rashes, insect bites, etc.
A spider needs to catch prey before it can create a bug “slurpee”. This is where the spiders other end comes into play. The spinnerets, from which a spider’s silk is extruded, are located in the abdomen. Spiders draw out the silk, which changes physically from a liquid to silk as a result of being pulled out. We tend to visualize the “orb” style of spider web when we think of spider architecture. These webs have a pattern of strands radiating out from the center, overlaid with a spiral. This pattern is actually produced by the most archaic family of spiders, Araneus – the “Orb Weavers”. When an unlucky insect hits the web, the spider, alerted by the vibrations of the struggling victim, rushes to it’s prey and quickly wraps it in silk. Once the insect is subdued, the spider will inject it with venom in preparation for feeding. Spiders are able to avoid getting stuck in their own webs due to several characteristics that they possess. Their feet, which are called “Tarsus”, have specially adapted hooks and bristles. These can be clipped and unclipped from the web strands, rather like a mountain climbers carabineer. The bristles are also coated with a non – stick coating which resists adhesion. Studies show that spiders minimize duration of contact when traveling across the web. Also, they minimize the surface area of their body that is contacting the web at any given point. By contrast, a flying insect will, for example, blunder into the web bringing much of its body in contact with the sticky strands, thus becoming trapped at several points.
A spider can also see its prey, as they possess eight eyes, which provide excellent vision as compared to other arthropods. Because of this advantage, other families of spiders have diverse strategies for hunting, not all of which involve trapping with webs. Jumping spiders, which have especially acute vision, stalk their prey and leap upon it. Wolf spiders of the Lycosidae family also rely on sight to stalk. They are commonly found in our woodlands, but are most active at night. They can be found during the day by looking under logs and other debris in the woods. The Six Spotted Fishing spider (Dolomedes triton), a native of wetlands in our area, demonstrates an interesting method of finding food. It can enter the water and hunt small fish, tadpoles, and other aquatic organisms. The oxygen trapped on its body by hair allows it to remain under the surface for an extended period while it stalks prey.
Spider procreation can be a rather dicey affair. Male spiders tend to be smaller than the females. In some cases this is to their advantage when approaching a prospective mate. They may be deemed so small as to be hardly worth the effort of killing and eating, and for that reason allowed to approach. The males of some spider species go through a courtship ritual to announce themselves as a suitor, not a meal. Perhaps this is so amusing to the lady spider that she forgets she’s hungry! Nonetheless, the male’s role is a dangerous one. He often does become a meal for his betrothed – before or after mating.
Females lay eggs, and they build a silk nest for the eggs to reside in until hatching. This may be in a web, or in the case of the previously mentioned Wolf Spiders, she will carry the eggs with her in a silken ball, under her body. When the young hatch, she continues to carry the spider lings on her abdomen until they are large enough to fend for themselves.
An interesting method that baby spiders of some species have of “leaving home” and dispersing themselves is called “ballooning”. They will climb to a highpoint, and release several especially fine strands of silk into the air behind them. These form a kite – like structure which is capable of carrying them quite a distance – perhaps even miles, from their launch point. Most spiders have short lifespan, living one or perhaps two years. Some members of the family, such as Tarantulas, live much longer – over twenty years.
We tend to think of nature and the natural world as being “outside”, but spiders remind us that nature does not always remain beyond the walls of our homes. The Brown house spider, Steatoda grossa, is the spider most often found indoors in our area. They make themselves at home right in our houses. Before you assume that’s a bad thing, examine the web of your resident spider closely. Although their webs are somewhat unsightly, they do perform some efficient pest control. You’re likely to find quite a collection of insect and other critter remains disposed of under the spiders trap. Those are bugs that would otherwise be wandering around your abode and up to no good.
Well, having established that spiders are rarely dangerous, and can in fact be beneficial, I feel a little better. How about you?
See you on the trails, and look out for that spider web!