1911.] NATURAL SCIENCES OF PHILADELPHIA. 397 



food and when sufficiently close they jump and seize the prey. They 

 use no snares whatever in capturing food. (2) The snarers catch their 

 food with snares and never hunt for it. (3) The tube-dwellers run to 

 the entrance of their tubes in order to catch the prey. These three 

 classes in the table (pages 386-393) are referred to as H, S, and T. 

 The hunters without exception have more compound organs than 

 either the snarers or tube-dwellers. The average number of compound 

 and simple organs and single slits for the hunters is 61-3-100; for 

 the epigaean snarers 58-4-99, and for the littoral and cavernicolus 

 snarers 51-6-119; but for snarers of all kinds 56-4-105; for the tube- 

 dwellers 49-5-144. Hence the number of single slits in both hunters 

 and snarers is the same while the number of organs varies considerably. 

 The cave forms have a few more single slits than either the hunters 

 or epigaean snarers, but their number of organs is much reduced. The 

 tube-dwellers have the greatest number of single slits, but the fewest 

 organs of all. The range for the hunters is 69-51 c. o., 7-0 s. o., 

 375-34 s. s. ; for the epigaean snarers 66-49 c. o., 11-0 s. o., 241-18 

 s. s. ; for the other snarers 59-42 c. o., 13-1 s. o., 217-51 s. s., but for 

 both kinds of snarers 66-42 c. o., 13-0 s. o., 241-18 s. s. and for the 

 tube-dwellers 50-48 c. o., 6-3 s. o., 237-60 s. s. The difference 

 between the maximum and minimum is practically the same between 

 the hunters, epigaean and cavernicolus snarers but when all the snarers 

 are compared with the hunters, the former vary much among them- 

 selves. The reason why there is such a slight range among the tube- 

 dwellers is perhaps because Caponia, Ariadna and Dysdera are the 

 only forms included here. 2 



All true cave spiders are snarers and it is manifest that the more 

 they have become adapted to a subterranean life, the more their 

 lyriform organs have degenerated. Thus to arrange them according 

 to the degree of such an adaptability, we have the following series 

 with regard to the number of compound organs: Th. kentuckyense 

 with 59, Th. porter i 58, Erigone 52, Troglohyphantes 50, Linyphia 48. 

 and Phanetta 42, of which series there is a gradation from the epigaean 

 Th. tepidariorum with 60 compound organs which nests in walls and 

 outhouses to Phanetta which is able to adapt itself to any place in a 



2 Calculus and Ammoxenus have not been included in the above comparison 

 because I have been unable to find any literature concerning their habitats. 

 Calculus bicolor, from South Africa, is a new species described by Purcell, and 

 its habits have not been described. Simon (1892) described for the first time 

 and created a new family for Ammoxenus from South Africa, but all he says 

 about the habitat is — "lis se trouvent a terre, dans les endroits decouverts, 

 et ils courent au soleil avec une telle rapidite qu'il est difficile de s'en saisir." 



