414 ABACHNIDA 



jointed, the terminal joint being a sharp claw, near the end of which is the 

 opening of a poison gland. The mandibles are usually directed downwards 

 so that the spider must strike when its prey is beneath it. The second 

 pair of appendages are the pedipalps or palpi, which are leg-like in form 

 and composed of six segments; the large and flattened basal segments 

 of these are called the maxillae or endites and extend forwards, forming 

 the principal jaws of the animals, being used to chew or squeeze the 

 food. 



In the male the end of the pedipalp is enlarged and bears the 

 more or less complicated palpal organ by which sperm is conveyed to 

 the female in the act of pairing (Fig. G53, C). The four pairs of long 

 walking legs are seven- jointed. The tarsus or terminal joint of each leg 

 bears a pair of claws, the inner edge of each of which is toothed ; in many 

 spiders a third smaller claw is also present and in others a thick brush of 

 hairs. Between the maxillae is a plate called the labium or lip, and 

 between the base of the legs is the sternum. The abdomen bears at 

 its hinder end, just in front of the anus, usually 3 pairs of spinnerets, 

 which are modified legs (Fig. 655). At the end of each spinneret are 

 minute tubes which are the ends of the ducts of the silk glands; the 

 fluid silk coming out of these tubes unites to form a single strand, and 

 hardens on exposure to the air. In a few families a plate called the 

 cribellum lies in front of the spinnerets from which spinning tubes also 

 project; such spiders have a row or comb of stiff hairs on each of the 

 hind legs called the calamistrum (Fig. 655) by means of which a band of 

 silk may be spun. All the spinning tubes do not exude the same kind 

 of silk, but a variety of kinds is produced which are used for various 

 purposes, as for making the different parts of the web, nests, cocoons, etc. 



Spiders are not well provided with special sense organs. The long 

 legs and the hairs usually covering the body are tactile organs, and in 

 most spiders eight simple eyes are present on the front portion of the 

 cephalothorax usually in two rows, enabling the spider to see a short 

 distance (Fig. 653, B). 



The respiratoiy organs of spiders consist of two pairs of lungs in 

 the Tetrapneumones, which are situated in the forward part of the abdo- 

 men and open to the outside by slit-like spiracles on the ventral surface; 

 in the Dipneumones one pair of lungs is present and a pair of tracheae, 

 the latter opening in most cases through a single spiracle in front of 

 the spinnerets. Each of the lung spiracles is covered with an integu- 



Emerton, 1902. "Families and Genera of the Araneida," by Nathan Banks, Am. Nat., 

 Vol. 34, p. 293, 1905. "Fauna of New England. A List of the Araneida," by Eliza- 

 beth B. Bryant, Bost. Soc. Nat. Hist, Occ. Papers, No. 7, 1908. "Catalogue of Neartlc 

 Spiders," by N. Banks, Bull. No. 22, U. S. Nat. Mus., 1910. "The Spider Book," by 

 J. H. Comstock, 1912. 



