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 nczvia (Ag-a-le'na nas'vi-a 
(Fig. 34). 
Family DlCTYNIDiE (Dic-tyn'i-dae). 
The Curled-thread 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 Dictynidcz. 
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 cribellmn (cri-berium); 
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 other 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. 
