32 THE STUDY OF INSECTS. 



of spinnerets are two-jointed, and usually longer than the 

 others. 



The common grass spider, which abounds in all parts of 

 the United States, is Agalena ncevia (Ag-a-le'na nas'vi-a 

 (F'g- 34). 



Family DlCTYNID^E (Dic-tyn'i-dae). 

 The Curled-tJircad Weavers with Irregular Webs. 



The Dictynids (Dic-tyn'ids). 



Certain spiders are remarkable for using two kinds of 

 silk in the formation of their webs. Thus, as explained 

 later, the Orb Weavers build the framework of their orbs of 

 dry and inelastic threads, and attach to this framework a 

 thread which is sticky and elastic ; while most spiders which 

 make irregular webs use only one kind of silk. There are, 

 however, certain species of irregular web-weavers which use 

 two kinds of silk. One of these is a plain thread like that 

 spun by other spiders, and the other is a peculiar curled 

 thread or a delicate band of tissue in which there are curled 

 threads. 



The curled-thread weavers represent two families, one 

 of which makes irregular webs; the other, those which are 

 of definite form. The first of these is the Dictynidce. 



The curled -thread or tissue-like band is made in the 

 same way by both families. It is composed of silk spun 

 from a special spinning-organ, situated in front of the 

 ordinary spinnerets, and named the cribellum (cri-bel'lum) ; 

 and is combed into its peculiar form by means of a comb of 

 stiff hairs, the calamistrum (cal-a-mis'trum), which is borne 

 by the metatarsus of the hind legs (see page 23). In mak- 

 ing the curled thread the spider turns one of its hind legs 

 under the abdomen so that the calamistrum is just under 

 the cribellum, and the foot rests on the ether hind leg. It 

 then moves its hind legs back and forth rapidly, so that the 

 calamistrum combs out from the spinning-tubes, and at the 

 same time tangles, a band of fine threads. 



