Spider
in zoölogy, the popular name of any individual of Huxley's Araneina.
The species are very numerous and universally distributed, the largest being found in the tropics. The abdomen is BIRD SPIDER without; distinct divisions, and is gen erally soft and tumid; the legs are eight in number, seven-jointed, the last joint armed with two hooks usually toothed like a comb. The distal joint of the falces is folded down on the next, like the blade of a pocket knife on the handle, and the duct of a poison gland in the cephalothorax opens at the summit of the terminal joint. There are two or four pulmonary sacs and a tracheal sys- SPIDER tem; eyes generally eight in number; no auditory organs have been discovered.
Their most characteristic organ is the arachnidium, the apparatus by which fine silky threads in the majority of the species utilized for spinning a web-are produced. In Epeira diadema, the common garden spider, more than 1,000 glands, with separate excretory ducts, secrete the viscid material of the web.
These ducts ultimately enter the six prominent arachnidial mammillæ, projecting from the hinder end of the ab-