id 
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 which will 
dissolve in water. 
Miss Thompson had frequently found burrows with doors that 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 pebbles 
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- 
ae doar spiders within their nests if it can find them, and it is a 
rantula : ; : 
Hawk, most formidable adversary, for 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 
upon the architectural’ habits of spiders. I have traced? the well 
Enemies known habit of the Tiger spider to cover its burrow with a 
ranenre 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 could only reason from analogy, but offered some conjec- 
tures* as to the character of the enemies whose assaults 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 
Mimicry 
of Site. 
1 Vol. IL., Plate V., Fig. 2; see also full description, pages 384, 385. 
2 See Vol. IT., pages 404, sq. 8 Td., 409. *Td., 414. 
