Pomona College Journ/U. of Entomology 863 



only a part of tliciii use it in (;a|it\irint? their prey, the former must have 

 been tiu' jiriiiiai'y utility, and this use varies in ainoiint from the few threads 

 of tlie Pholcus to the elaborate e^g sae of tlie (iiyptocranium cornigerum. 

 Some of the more speeialized ways of utilizing the silk, are by the burrow 

 spider for strengthening the walls of the tunnel or by the trap-door spider in 

 its speeialized lid, or the Ariadiia in its remarkably contrived tube. Nothing 

 can be said definitely as to the way in whieh the web-making habit arose, but 

 it seems probable that the spinning (jf :i di'ag line was one of the first steps, 

 and the next is not difficult to iiiiaginc Working in a limited space, the 

 spider would cross and recross this line till som(;thing of a web was formed, 

 and if perchance an insect were entangled in it, the process would be complete. 

 The simpler webs, such as that of the I'holcus. are just those irregular nets 

 made of the same kind of silk as the drag line. In advance of the I'liolcus are 

 the Linyphiidte, the sheet web weavers, and the Agelnida; with the addition 

 of the funnel-shaped retreat. All of these webs, formed of one kind of silk, 

 are simply to entangle the insects until the spider can reach them, but during 

 the evolution of the web-making habit, many families have developed special 

 organs for producing a visciil silk for holding the insect fast. The Theridiidie 

 have the simplest form, a viscid liciuid tlirown over the prey, but there is a 

 specialized organ, the com)) on the tarsus of the fourth legs, for flinging the 

 silk. Other families use a thread or band of the viscid silk in making the 

 web and in these webs of combiued materials, two lines of specialization are 

 recognized. The first is a siiiijile foundation and a complex structure of the 

 viscid which may be a simple or complex hackled band. The second, a per- 

 fected foundation and an unspecialized use of the viscid silk, finds its culmina- 

 tion in the orb- weaving spiciers, the lUaboridai and the Argiopidie. The steps 

 in the building of an or!) web are very interesting. First the outer frame- 

 work, the permanent part, is made, and then in the open si)ace thus formed the 

 radii are stretched. At their converging point the hub is erected and from 

 this a spiral guy line is spun upon the radii, to hold them together for the 

 next process. After all this has been formed of dry silk, beginning at the 

 outer edge, the spider adds the loops and turns of viscid silk, destroying the 

 spiral line in the process. The remainder of the article is devoted to examples 

 of orb-weaving spiders of different kinds and closes with a tabular arrange- 

 ment of the steps in the perfection of web-making. 



Elizabktii Jacks. 



THE Si'lDEK BOOK 



J. H. COMSTOCK 



Doubleday, Page & Co. 



To the general reader as well as to those more particularly interested in 



zoology, this book must be of interest. The subject matter covers over 705 



pages and there are also over TOO illustrations. Much of the material included 



is new and all is clear and well presented. Among the interesting material 



