Purse Web Spider: How to Identify this Spider -

The Purse web spider is one of nature’s fiercest ambushing arachnids. But how these primitive spiders, mygalomorphs, capture and kill their prey also makes them one of the most fascinating spiders in the world. So, let’s begin there.

Purse web spider tube — A purse web spider’s tube. (Via: Wikimedia Commons)

Purse web spider: The aerial web.

What you are looking at is the tip of the iceberg, so to say, of the purse web spider’s only way to catch their next meal. This is an aerial web, a tube that protrudes above the purse web spider’s retreat. Just below the surface, the spider waits in its underground den.

The purse web spider builds its aerial web by fashioning a web tube with its silk that hangs vertically (except for the black purse web spider’s, which runs horizontally) against a tree or rock. After weaving the tube, the purse web spider camouflages it by covering its surface with lichen, bark, and other local bits of local material and debris.

When an insect crawls over the tube, the purse web spider races up and pierces its abdomen from below with her fangs.

The fangs of a purse web spider are as unique as their aerial webs and likely why the spider has to use the manner of hunting their prey. A purse web spider’s fangs only move up and down, so they cannot pinch their prey like a normal spider. Therefore, using an aerial web to pierce a victim from below makes perfect sense.

The protection that using such a web gives to a purse web spider is considerable. Purse web spiders rarely venture out of their lairs for anything except mating. To remain inside and protected, the purse web spider even adapted a clever way to dispose of its trash.

After the purse web spider has killed her prey with her fangs, she cuts a slit in the tube, pulses the victim inside, and then immediately reseals the opening. When she’s finished her meal, she simply climbs to the top of the aerial web and tosses the garbage onto the forest floor below.

Purse web spider: Mating and reproduction.

Have some pity for the male spider; he risks everything to reproduce and is often killed by his much more aggressive and larger mate. The purse web spider male is no different. Lured by the female’s pheromones, he cannot resist—even though the odds are stacked against him.

The male purse web spider must first risk exposure to predators while trying to find a female’s aerial web. When he finds one, things get really dicey for him.

The first thing the male purse web spider does is tap on the aerial tube in an attempt to notify the female he is a potential suitor– not an insect or other prey. If the female inside has already had her eggs fertilized, isn’t mature enough to mate, or isn’t in the mood—the male is killed and eaten.

Oops!

However, if the female purse web spider is willing to mate, she will allow him to enter through the top opening of the aerial web. After they breed, the male stays with the female for a few months before it dies of natural spider causes. Then he is eaten.

Male spiders, am I right?

The female purse web spider will create egg sacs on the bottom of the aerial web for about a year until they emerge. Purse web spiderlings hatch in late summer, and the mother usually stays with them through the winter until they disperse in the spring.

More about the poor, male purse web spider.

The Missouri Department of Conservation gives a some interesting tidbits of knowledge that I could not find another source for, so, here it is verbatim.

“The red and black coloration of S. rufipes and S. fitchi males may be an example of Batesian mimicry, in which a relatively harmless or helpless species benefits from a resemblance to species (such as ants or wasps) that can sting. The fact that only the males — which must leave the shelter of their tube webs and risk their lives walking around in the open — have this coloration supports this theory.

Herbert Fitch, who collected the type specimen for the purseweb spider that bears his name, observed a jumping spider pounce on and kill a same-size specimen of S. fitchi. The acuity of senses, rapid movements, and ease with which the jumping spider dispatched the purseweb spider led him to note that male purseweb spiders must be extremely vulnerable and experience a high mortality once they leave their tube shelters and go out in the open looking for females.“

Again, I have nothing but pity for the male spider of any species. However, the male purse web spider has at least one protective (red legs) adaptation.

Purse web spiders: Description.

Purse web spiders are medium-sized, dark-colored spiders notable for their oversized jaws. These spider spiders stand in squat like fashion with their legs sprawled. Female purse web spiders have a bodies about 1 1/4 inches in length.

Purse web spider: Diet.

Purse web spiders do not eat a lot of flying insects, mainly because such bugs do not land frequently on their aerial webs. Instead, the purse web spider eats beetles, caterpillars, crickets, ants, other spiders, millipedes, and sow bugs.