BEHAVIOR OF SPIDERS AND OTHER INSECTS 409 



the drag-line. The web of Pholcus is a good example. The 

 webs of the sheet-web builders aie constructed of this kind of 

 silk; but they have a more or less definite form. Slightly higher 

 than these and constructed of the same kind of silk are the 

 webs of certain members of the Agelenidae, which have a defi- 

 nite shape and a funnel-shaped retreat. These webs of dry 

 silk simply impede the progress of the insect and enable the 

 spider to capture them. To assist in holding the snared insects, 

 many spiders secrete a viscid silk. Among the webs constructed 

 in part of viscid silk there are evidences of evolution. The 

 webs of the Theridiidae are almost as simple as those of Pholcus; 

 but the inmate swathes a viscid fluid about its prey. Other 

 spiders construct viscid bands or viscid threads in their webs. 

 Of these webs there are two types; one in which the portion 

 constructed of dry silk is comparatively generalized and in 

 which the viscid silk is supported by a specialized band; and 

 another in which the foundation of dry silk is highly specialized 

 and in which the structure of viscid silk has remained compara- 

 tively simple. In each class the webs may be arranged in a 

 series indicating the path of evolution. Since this viscid fluid 

 is produced by the lobed glands in the Theridiidae, by the 

 cribellum glands in the Cribellatae, and by yet other glands in 

 other spiders, Comstock claims that this viscid fluid has arisen, 

 independently, at least three times. In addition to describing 

 the web-building behavior of spiders, Comstock gives a key for 

 recognizing groups of spiders by their webs. 



Weiss (106) describes the egg-laying of Lixus concavus. 



Matheson and Crosby (58) describe the oviposition of Limno- 

 dytes gerriphagus Marchal and Caraphractus cinctus Walker. 



Pierce and Hollo way (73) state that Chelonus texanus Cress, 

 deposits its eggs in the egg of the host insect ; but that the para- 

 site emerges from the larva which develops from the egg. 



FOOD-PROCURING AND DEFENSIVE INSTINCTS 



Campion (14) describes the feeding habits of the scorpion 

 flies; Cockerell (17) of Dysdercus mimus Say; Hungerford and 

 Williams (42) of the young of Ammophila sp.?, Chlorion caeru- 

 leum Drura, Trypoxylon texensts, Crabo mterruptus St. Fargo, 

 Odynerus annulatus Say, O. geminus Cress., Halictus niaculi- 

 frons, Dianthus concinnum; Moore (62) of a large number of 



