BIOLOGICAL MISCELLANY. 75 



proportion, until she has made her fifth lid. In this the inside alone is 

 lined, and all the rest is made of clay and a sort of glue or mucilaginous 

 material, which the spider secretes from its mouth parts, and whicli will 

 dissolve in water. 



Miss Thompson had frequently found Ijurrows with doors tliat were 

 bare and others covered with lichens, according to the ^condition of the 

 bank on which they were located. She had never in a single 

 }^\ ^^ instance found a nest on a lichened hillock that did not con- 

 tain lichens upon the lid. She had cut the upper portion of 

 many from the ground in order to preserve them, and after the door was 

 thoroughly dried the lichens usually fell off. She had not seen the spiders 

 in the act of fastening on the plants, but had no doubt that in some 

 way this was accomplished, or at least permitted. 



Mr. Titus avers that Cteniza attaches moss, sticks, and fine pebldes 



to her door at times, and her object in so doing he believes to be to 



hide it from the " Tarantula hawk." This insect attacks Trap- 

 The Ta 



^ , door si)iders within their nests if it can find them, and it is a 

 rantula ^ ■ i , i i n ■ ■ ■, 



Hawk most formidable adversary, lor it grows to be about two inches 



long. Mr. Titus had the impression, which is the popular one, 

 that the Tarantula hawk feeds upon the Trapdoor spider ; but by reference 

 to Vol. II. of this work it will be seen that the object is simply to pro- 

 cure food to place within a cell wherein the wasp bestows the egg of her 

 future offspring. The insect referred to by Mr. Titus is no doubt the 

 so called " Tarantula killer " of the southwestern States, the beautiful Pepsis 

 formosa Say, which I have figured,^ and whose habits in connection with 

 the destruction of the large hairy Tarantula I have fully described. 



This observation proves most interesting, and confirms in so far what 

 I have said of the reactionary effect of hostile agents and environment 



ujwn the architectural habits of spiders. I have traced'-^ the well 

 Enemies Jjuq^v^ habit of the Tiger spider to cover its burrow with a 

 A. V^?^*^® mossy vestibule to which is attached a rude sort of door, to the 

 ture purpose to protect itself from the attacks of an invading wasp, 



Elis 4-notata. I had no hesitation^ in using the knowledge thus 

 furnished by the habits of Tigrina as a key to interpret the motive power 

 of Trapdoor spiders in their remarkable industry. I had no facts in my 

 possession, and coukl only reason from analogy, but offered some conjec- 

 tures* as to the character of the enemies whose as.saults are thus met by 

 this rare counteracting ingenuity. I also ventured to predict, from the 

 various facts alluded to, that the " enemies they most dread may be rea- 

 sonably looked for among diurnal creatures, and not among those of 

 nocturnal habits." The observation of Mr. Titus, which is unfortunately 



' Vol. II., Plate v.. Fig. 2 ; see also full description, pages 384, 385. 



2 See Vol. II., pages 404, sq. ^ Id., 409. ^ Id., 414. 



