About Spiders

   All spiders are predaceous and feed on insects, which they entangle in their snares and webs, or stalk, or catch after patient lurking. In most cases they kill their prey with their poisonous fangs. The mouth is small, and behind the gullet there is a powerful suctorial region which acts as a suction pump. From the midgut five paired outgrowths extend into the bases of the pedipalps and legs. There are also large tubular digestive outgrowths, and two excretory Malpighian tubes grow out from the hindgut. The heart lies dorsally in the abdomen, and has three chambers with three pairs of valved openings.

   The sexes are separate except in a few casual hermaphrodites, and the males are often fewer in number, always smaller in size, and usually more brightly colored than the females.

   The eggs are deposited (10 to 2000 in number) within silken cases or cocoons made by the mother spider for this purpose. As the young spider grows it is obliged to molt the skin. The number of molts varies from six to nine. The spider's silk is not used solely in the construction of webs but serves a variety of purposes. With many spiders the web is a loose, irregular maze of crossed threads, which are the true cobwebs. In other cases it is a flat sheet of threads with a tubular retreat at one corner. The geometric or orb webs consist of a varying number of radiating lines crossed by many parallel or spiral threads. The whole is supported by several guy lines or stouter threads. At one corner or in the near vicinity is a silken nest or retreat, where the spider remains concealed during the day or when not using the web. This retreat is connected by a line to the center of the web. When waiting for prey the spider rests upon the center of the web, head downward and legs extended.

Black window spider