136 AMERICAN SPIDERS 



leave the nest in the late summer and disperse by ballooning. Their 

 threads are usually a heavy band of parallel strands less fine than 

 those of true spiders. Some of the young, it is thought, do not take 

 to the air but merely walk a short distance from the maternal nest 

 and begin work on tiny tubes of their own. 



The purse-web spiders are the most extraordinary of all the 

 atypical tarantulas, as regards both their physical features and their 

 singular habits. The marks of their primitive origin are clearly 

 shown in the presence, above the base of the abdomen in each sex, 

 of a single well-marked tergite, and the considerable separation of 

 the anal tubercle from the posterior spinnerets. In the reduction of 

 their cardiac ostia to three pairs is clear evidence that their heart 

 has become specialized, or simplified, at a much faster rate than 

 have other features of the abdomen. The chelicerae, though not 

 provided with a rake for digging, are modified into effective shov- 

 els for carrying loads of sand or pellets of soil. The fang is a long, 

 thin spine well designed to pierce the silk and hold the prey. 



The species of Atypus are found in the north temperate zones of 

 Europe, Japan, and the eastern United States. Species are also known 

 from Java and Burma in the eastern tropics. Another genus of the 

 same family is Calommata, which is largely restricted to tropical 

 areas in Africa and the Orient. The four American species of 

 Atypus are all confined to the eastern portion of the United States, 

 and are most abundant in the extreme southeastern part of their 

 range. Only three of our species are well known, and only two of 

 these moderately common. 



The females of all the American species are predominantly brown 

 in color, shining, and only very sparsely set with covering hairs. 

 The robust body is provided with quite short legs and long chelic- 

 erae, and runs about half an inch in length although bicolor, the 

 largest known species is often an inch in length. The males are 

 similar to the females in most respects, but have longer legs. In 

 niger, a shining black spider most closely related to the European 

 species, the disparity in size of the sexes is not particularly marked; 

 but in the other species the males are somewhat smaller than their 

 females, and very brightly colored. The abdomen of Atypus abboti 

 is a beautiful iridescent blue or purple, set against black legs and 

 carapace. Atypus bicolor has carmine legs, which, contrasting with 

 its deep-black carapace and abdomen, make it the most striking of 

 all our species. 



