1888.] NATURAL SCIENCES OF PHILADELPHIA. 211 



5. Doors. — An examination of the numerous nests shows that 

 openings are usually but not always left at the top of the tube. 

 These openings are placed indifferently beneath, at the side and 

 above. When the spider is not near the upper portion of its tube, 

 the silk naturally collapses, and the opening is not apjjarent. How- 

 ever, it must be remembered that a very slight stroke of the mandi- 

 bles would open the tube at any part and give the spider egress. 

 So also a few movements of the spinnerets would close the aperture. 

 Moreover, if we accept the conclusion that the mode of capturing 

 prey is the same as that of Atypus piceug (as above described) there 

 appears to be no special need for a door for the main necessity of 

 life, since the spider has little or no occasion ever to go outside her 

 own tower or cave. 



IV. SANDING THE OUTSIDE OF THE TUBE. 



It has been stated that one of the individuals put under observa- 

 tion, after having spun her snare, covered it more or less thickl}'' 

 with grains of sand. It Avas thus indicated that the sanded condi- 

 tion of the tubes found in natural positions is the result of purpose 

 on the part of the builder. What purpose does it serve? Many 

 spiders of various fiimilies are in the habit of protecting their cocoons 

 or eggsacs by covering them with mud, with particles of soil, with 

 bits of decayed wood and bark scraped or broken off, with various 

 minute chippage, and even with the debris of insects' wings, heads, 

 legs etc., captured for food. In this behavior the purpose is obvi- 

 ously to protect the enclosed eggs from hurtful weather changes and 

 various enemies, cheifly the parasitizing ichneumon-fly, Pezomachus. 



The use of the sand deliberately placed upon the outside of the 

 nest of Atypus is not so obvious, although it perhaps serves to 

 toughen it, and jiossibly protects its inmate from the assaults of 

 certain enemies as yet unknowm. In natural site the sand and 

 weathering give the tubes almost the exact appearance of the out- 

 side of the tree along which it is placed. In a large proportion 

 of my specimens the sand was intermingled with brown wood-dust 

 from decayed bark and the dark colored vegetable mold which was 

 heaped around the base of the trunk, and into which the spiders 

 had excavated. 



It has been conjectured that this is an example of so called mimi- 

 cry. Some observations made by Mr. Frederick Enock on the 

 habits of Atypus piceus, the British congener of our Florida spe- 

 cies, raise a doubt upon this supposition, at least indicate another 



