Spiders
Spiders’ role in the food chain
Spiders are largely insectivores and play an important role in keeping the insect population in balance. Spiders are not only an important food source for many other animals higher in the food chain but their webs provide nesting material for many bird species. In terms of their place in the trophic level, they would be classified as secondary consumers as their prey is usually primary consumers.
Spider venom
Most spiders are venomous and produce either cytotoxic or neurotoxic venom. Of the venomous species only a few are a threat to man. A pair of glands stores venom in sacks in the cephalothorax. Muscles surrounding the sacks contract forcing the venom along narrow tubes to the tip of the fang. The effect this venom has on humans depends on:
the age and health of the person;
what part of the body was envenomed (extremities are not normally as serious as the face, neck and torso);
the quantity of venom injected;
the person’s reaction to that type of venom (each person has a different reaction to venom).
The venom has two functions: one is to kill or paralyse prey and secondly it begins breaking down the internal organs of the prey. The spider then sucks out the juices.
First aid for serious neurotoxic bites is:...
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