220 AMERICAN SPIDERS 



leap away from a building and catch insects in flight, a feat that 

 demonstrates the remarkable co-ordination of their senses and their 

 superiority among spiders as hunters. 



The jumping spiders spin retreats of thick, white, slightly viscid 

 silk in crevices, under stones on the ground, under bark, or on foli- 

 age and plants. Many retire to these little white bags at night and 

 during cold days, and also use them as headquarters for molting and 

 passing the winter as juvenile or hibernating adults. The females 

 lay their eggs in the retreats, usually in spring or summer, and may 

 be found guarding their young after the hatching. Often many re- 

 treats are found grouped close together under a single stone. 



The salticids abound mainly in tropical regions. There live a 

 bewildering number of different types, many of them glittering like 

 gems in an infinite variety of patterns. Although less abundant in 

 the United States, about three hundred different species occur, and 

 many types penetrate far into the north. The jumping spiders live 

 for the most part on vegetation. A characteristic element of the 

 leaf mold of the whole temperate zone is the tiny, smoky-gray 

 species of Neon, whose greatly enlarged dorsal eyes shine out of a 

 body only one tenth of an inch long. R. W. G. Kingston, the 

 British naturalist, found a plainly marked jumping spider 22,000 

 feet up on Mt. Everest, a height at which few animals of any kind 

 can live. Tolerant in another way are the few species that have be- 

 come domesticated. The graceful zebra spider, Salticus scenicus, 

 hunts on fences and the walls of buildings, and is as common in 

 America as in Europe. 



A number of jumping spiders exhibit such an amazing resem- 

 blance to ants that they are called "ant-like" spiders. In the begin- 

 ning these spiders, probably through mere chance, gained a super- 

 ficial resemblance to ants by developing slender, cylindrical bodies 

 and quite long legs. (In the same way, other salticids became 

 plump, and came to resemble certain flea-beetles through the short- 

 ening of the body into a globular form.) It is only natural that 

 these spiders should run over the soil or vegetation much as the 

 ants do sometimes even in association with the latter. Within the 

 United States are found various distinct types that show different 

 degrees of physical resemblance to ants. There are profound dif- 

 ferences in structure between the two, and even the most antlike 

 of spiders does not bear too favorable a comparison with an ant 

 when parts of the body are closely studied. However, it is an en- 

 tirely different matter when the spiders are alive and moving. Then 

 they exhibit such an exacting simulation of ants that they are able 



