318 NORMAN E. M'INDOO. 



No. of Specimens. Relative Humidity. Hrs. Min. 



4 3836 3 15 



706659 5 30 



I 383644 8 15 



4 6393 8 15 



i 95828488 9278 23 35 



I 816076731007589 31 45 



.1 ioo 65 55 60 72 66 60 33 45 



On various dates at the entrance and at the different localities 

 in the caves the relative humidity was recorded. At the entrance 

 it varied considerably on different days, but in the caves, the 

 hygrometer always stood at ioo (saturation point). 



These arachnids always live in a saturated atmosphere and it is 

 impossible for them to survive long outside the caves where the 

 variation in the degree of humidity is great. As a general rule 

 the higher the relative humidity (with but a gradual and small 

 amount of variability), the longer they live. Since the above 

 experiments were prosecuted from May 18 to June 8, when the 

 change in temperature was not such as to materially affect these 

 spiders, we must attribute their deaths to the hygrometric 

 conditions. 



SUMMARY. 



1. Troglohyphantes cavernicola Keys, is found everywhere in 

 these caves, where the three following necessary conditions 

 exist total darkness, a saturated atmosphere, and a suitable 

 place for the construction of snares. 



2. The first pair of legs are used as tactile organs. 



3. All small winged insects, thysanurans and small myriopods 

 serve as food. Scarcity of food does not entirely limit their 

 distribution. 



4. They have no known enemies other than themselves. 



5. While temperature outside the caves does not materially 

 affect the adult spiders themselves, it is probable that to the 

 even temperature at localities between 600 and 1,700 feet from 

 the entrance is due the great number of specimens found at this 

 place. 



6. Courtship is similar to that of some outside forms. 



7. Cocooning is rudimentary. The eggs are few and com- 

 paratively large. 



