In Praise of Spiders

I enjoy watching spiders but admit to being a bit reluctant about picking them up. Although humans tend to be arachnophobes, due either to intrinsic or learned attitudes, we must admit admiration for the amazing design and adaptations of the numerous spiders we encounter every day. One of my favorites is the fishing spider that is common in our farm ponds (photo top left). It darts around on the surface of the water without sinking and can even catch prey under the water (here it has captured a larval dragonfly). Its hunting technique is primal in that it simply chases down its prey. Indeed there is a large group of “wolf” spiders that hunt in this fashion. One can imagine that this could represent the primitive condition in spiders before they developed the ability to make silk that could be fabricated into webs. This silk is a quite remarkable concoction of protein and other substances which has made spiders extremely successful and the subject of study by scientists interested in making similar polymers for human use.

Perhaps the most highly evolved spiders are also common in our yards, the orb weavers (photo top right). They construct an intricate circular structure of silk, some sticky and some not, to catch and ensnare their prey. The spider shown is a night hunter, which builds and removes its web every night, and must thus be very susceptible to predation by birds. It can sit in one place and hope to catch a night-active insect such as the conhead katydid (photo bottom left) which is well camouflaged to blend in with the leaves to protect against daytime predators, but has no defense against the web of this spider (see photo, bottom right, of spider eating a katydid).

So how do spiders try to avoid being eaten themselves? Many are quite cryptic and hide during the daytime. The few that show themselves (such as golden garden spiders and banana spiders) must have mechanisms to avoid being eaten by birds. This could include large size and a venomous bite (although the most poisonous black widows are quite shy and retiring). Orb weavers may also hide off the web and only come out when prey is captured. One of the most interesting facts is that some daytime orb weavers often have highly visible structures in the webs (white patches of silk) that actually advertise the web- this is thought to be a means of warning birds not to fly through the web and thus destroy this valuable resource.

So throw aside any bias you may have against these hairy critters with eight legs, and just enjoy the amazing spiders.

Bill Dunson, Englewood, FL & Galax, VA
wdunson@comcast.net