2o8 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



spider, the female of which has a round abdomen that is 

 marked on the underside by a bright red spot, usually hour- 

 glass shaped. The slender abdomen of the male has three 

 light spots or dashes along the median line and three or four 

 lateral stripes. The very young of both sexes have little 

 black on them and immature females are colored much like 

 the males. This species is cosmopolitan. In the United States 

 it occurs as far north as Massachusetts but is more common in 

 southern regions. These spiders are found in the fields on 

 plants or among loose stones and around houses in dark 

 corners or in boxes or rubbish. 



The webs that spiders spin for traps to ensnare their prey or 

 to line their nests or to protect their eggs are made of silken 

 threads of various sizes. Some of these threads are composed 

 of several finer threads united. Spiders produce several kinds 

 of silk, one kind being always viscid and sticky. Most 

 spiders have three pairs of spinnerets, a few having but two 

 pairs, situated at the tip of the abdomen. On the ends of 

 these short finger-like spinnerets are many minute openings 

 through which the fine silken threads are drawn. These 

 openings lie in little papillae, called spinning spools and 

 spigots. When the tips of the spinnerets are placed close 

 together, the issuing threads all unite into a large strong 

 thread. If the spinnerets are held further apart the broad 

 silken bands are produced. 



The great hairy tarantulas of our southern and western states 

 line their burrows with a thin layer of silk. The trap-door 

 spiders usually make a heavier lining sometimes dense and 

 tough, but with a smooth soft silken surface. The door that 

 these spiders make to guard the entrance to their burrow is 

 made of silk and earth, leaves, grass or moss, always resembling 

 closely the ground or ground-covering around it. The com- 

 mon black running spiders that often carry their egg sacs with 

 them and the stout-bodied little jumping spiders which leap 

 on their prey, spin but little web. 



The sedentary spiders, or those which spin webs of various 

 sorts to capture their prey, include most of the common kinds. 

 The cob- web weavers, which are one of the trials of the house- 



