160 AMERICAN SPIDERS 



often claim space beneath the soil by digging a tunnel; and the 

 water spider has invaded the fresh water with great success. Above 

 the ground, the vagrants move on all types of surfaces and climb 

 into shrubbery with great agility. It may be seen, therefore, that 

 they live side by side with the aerial spiders, but both are neverthe- 

 less to a large extent insulated from each other, almost as if they 

 were in two worlds. King in its own domain, the hunter is usually 

 a weakling in the clutching web of the sedentary spider. Outside 

 its web, the sedentary spider is no fair match for the average hun- 

 ter. The superiority of either line can never be tested except in 

 terms of which one shall give rise to the dominant spider of the 

 future. Both have accomplished great things, and stand as equals 

 that have reached their goals by different roads. 



THE PRIMITIVE LINE AND SHEET WEAVERS 



The members of this group can be regarded as a major segment 

 of that series that took to an aerial life. They resemble in general 

 features and equal in developmental rank the primitive hunters and 

 weavers. For the most part, they are pale spiders that live in dark 

 places, there laying down a relatively simple web of dry lines or 

 sheets and relying on this to secure their livelihood. Most are little 

 changed from the presumed ancestral types. The palpi and epigyna 

 are quite simple, though in one family, the Pholcidae, they appear 

 to be specialized by numerous processes that largely mask the other- 

 wise generalized nature of the organs. The posterior respiratory 

 organs are tracheae. In the Telemidae are two openings to the 

 tracheal tubes, but in the other families only a single one is present, 

 the usual position being well in front of the spinnerets. The chelic- 

 erae of the Pholcidae are soldered together along the midline as in 

 the Scytodidae and related families, but in the other members of 

 the series they are free. Males and females are quite similar in size 

 and appearance; often they are found living amicably together in 

 the webs. During the mating, the pholcids insert both of the palpi 

 simultaneously, as do most of the primitive hunters, and the stance 

 is the generalized type of that group. Little is known about the 

 mating habits of other members of the series. 



The line weavers of the family Pholcidae (Plates VII and XIX) 

 have small globose or elongate bodies suported on exceedingly long 

 and thin legs, a physical feature that causes them to be mistaken for 



