THE TRANSACTIONS OF 

 THE SECOND ENTOMO- 

 LOGICAL CONGRESS, 1912. 



THE SILK OF SPIDERS AND ITS USES. 



By John Henry Comstock, Ithaca, N.Y., U.S.A. 



(Plates III, IV, and V.) 



While silk is produced by the representatives of many orders 

 of animals, it is in the order Araneida that the production of this 

 substance has reached its highest development. Not only do 

 spiders produce much silk, but they use it for widely different 

 purposes ; and there have been developed in these animals 

 several different types of silk glands, each of which produces 

 a special kind of silk, fitted for a particular use. 



The most extended study of the silk glands of spiders that 

 has been made is that of Apstein (1889). This writer showed 

 that at least seven diñerent types of siik glands are to be found 

 in spiders, although no spider possesses all of them. These 

 glands are designated respectively as the aciniform, pyriform, 

 ümpullate, cylindrical, aggregate, lobed, and cribellum. 



In the four-lunged spiders only the pyriform glands have 

 been observed ; but only a very limited amount of study has 

 been devoted to the silk glands of these spiders. In all two- 

 lunged spiders studied, three of the seven types of glands have 

 been found ; these are the aciniform, pyriform, and ampullate. 

 A fourth type, the cyhndrical, is wanting in only two families, 

 the AttidcB and the Dysdcridce. The three other types of glands 

 are each characteristic of a particular group of spiders. The 

 I 



