One Spider's Method to Prevent Overeating
Changing the Web Architecture Prevents Insects from Being Caught
The widow spiders are so named because the females often eat their mates – sometimes before they have mated. The every-day feeding behavior of widow spiders suggests that this behavior may be inflexibly hard wired into their neural pathways. These and a few other spiders also bite humans frequently enough and cause enough injury to give all spiders a widely feared reputation of causing pain, injury, and death to humans. This reputation is not really warranted as most spiders do not or can not bite humans, restricting their biting to capturing and processing prey, and even if they did bite humans, there is little damage done.
Web Organization
For most web building spiders the web defines the limits of their territory and serves a multitude of functions. The web is a place to capture food, eat, mate,raise offspring, rest, hide, and escape predation, and different areas of the web are, in general established for each activity. For many spiders, the locations where the several activities take place are clearly defined and the resident moves between these locations in response to her/his momentary needs.
For other species, the boundaries of the trap, nursery, dinner table, bedroom, and refuge are less evident and any of these activities can occur almost anywhere on the web. The widow spiders (Latrodectus sp.) fall into this second group of spiders. Instead of constructing organized webs like the orb weavers, widows produce a loose, three-dimensional network of fibers with seemingly erratic strands stretched randomly across its space. To the spider, these strands serve as pathways to and from several poorly defined activity centers. to other organisms, they serve to slow down travel and reduce the possibility of a predator penetrating the tangle of threads this spider calls home.
Organization in Chaos
The widow's web has two configurations that vary significantly based on whether the resident is hungry or not: tangle and sheet. When not intent on feeding, these spiders' webs are composed of a dense tangle of threads that extend randomly through the entire web space. None of the threads in this web are sticky. This version of the web is used primarily for resting, escaping predation, mating, and raising babies.
The sheet web configuration is produced when the spider needs to feed. At this time, it creates a capture area by removing many of the lowest strands of the tangle web and filling the now empty region with a sheet of about thirty vertical strands of sticky webbing. The spider now spends much of its time in the tangle just above the sheet. When an insect bumps into and adheres to the threads, the spider drops down from the tangle and bites the insect. The venom in the spider's bite rapidly immobilizes the insect while the digestive enzymes convert muscle and other tissues to liquid. The spider immediately begins to feed on the insect's juices. Once the prey has been drained, the spider cuts the empty exoskeleton from the web, and discards it.
If the spider is still hungry, she leaves the sheet of sticky threads hanging and retreats into the tangle to wait for more prey. If she has become sated, she cuts the sheet of sticky threads from the web and replaces them with a tangle of non-sticky threads – reestablishing her fortress against predation.
An experiment on the effect of moving hungry and sated spiders from one web type to another is discussed on page 2.
Widow Spider in Web
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