THE AERIAL WEB SPINNERS 171 



numbers of genera and species the total for any comparable group 

 in the temperate zones; they are the dominant aerial types. Most 

 of the species are small, even minute, and they occur in vast, little- 

 noticed numbers under soil debris. As a group they have more 

 elongated bodies than the comb-footed spiders, and their legs are 

 set with long spines. Few of them become the obese lumps so fre- 

 quently found among the orb weavers; many run over the soil with 

 a speed that belies their dependence on a fixed space web. Their 

 chelicerae are large, strong, and well-toothed, the straight maxillae 

 little if at all inclined over the labium. The presence of stridulating 

 organs, most frequently a file on the side of the chelicerae and a 

 scraping spine on the femur of the palpus, further differentiate them 

 from the orb weavers. 



Sexual dimorphism is not pronounced, except in the species 

 with modified heads, and there is often considerable similarity in 

 size and coloration of the sexes. Male and female live peaceably 

 together in the webs during the summer months. 



Most linyphiids are rather plainly colored, but there are no- 

 table exceptions; some are carmine red (Ceratinopsis), and many 

 have distinctive dark patterns on light bodies. As is true of most 

 sedentary spiders, especially of those that live in dark situations, the 

 eyes are small, and little used, if at all, for the location and capture 

 of prey. Linyphiids for the most part prefer the shade, conse- 

 quently they live hidden away in dark places under natural debris 

 on the ground, or beneath the leaves of living trees. Many species 

 dwell in caves or animal burrows, and have in certain instances 

 partially or completely lost the eyes. 



The linyphiids are divided into two principal groups, which, 

 quite distinct in their extremes but completely bridged by inter- 

 mediate forms, are placed by many araneologists in separate fam- 

 ilies. The first of these, the Linyphiinae, includes the largest species, 

 as well as numerous spinners of extraordinarily beautiful webs. As 

 regards physical characteristics, the pedipalp of the female usually 

 retains the tarsal claw, and the palpus of the male lacks tibial apoph- 

 yses. In general the legs are longer and thinner, and are set with 

 more numerous spines than those of the Erigoninae (the other 

 principal group); and the tibiae are almost always furnished with 

 dorsal and lateral spines. Many small species belong in this group, 

 but space allows mention of only a few of the larger representatives. 



One of our largest and best-known linyphiids is the filmy dome 

 spider, Linyphia marginata, which abounds in temperate North 



