i 9 2 THE POPULAR SCIENCE MONTHLY. 



not to be cheated out of its proposed domicile, Stothis proceeded 

 to erect a cylindrical case about two inches long, composed of a 

 conglomerate gathered from surrounding particles of soil and 

 vegetable chippage. These were cunningly wrought together, 

 the whole structure silk-lined, and the characteristic trap-doors 

 hung, one at either end. Thus, while varying her habit in so far 

 as to build a surface tunnel instead of a subterranean one, Stothis 

 preserved her defensive habit of erecting for herself a back door 

 by which she could retreat in case of invasion at the front door. 



The burrow of Stothis cenobita (Simon) is simply a rounded 

 chamber underneath the surface, and closed by a trap-door, which 

 differs in no particular, as far as I can observe, from the ordinary 

 trap-door of the American Cteniza californica. 



It is difficult to say what may be the enemies of the trap-door 

 spider against which such ingenious architecture has been reared 

 and such vigilant watch is exercised. But the quite general testi- 

 mony is that these spiders leave their tubes at night and go forth 

 in search of prey ; or, as in other cases, open the lids of their 

 tunnels and spread straggling lines near by, upon which passing 

 insects are entangled and delayed long enough to allow the spiders 

 to pounce upon them from their open caves. If we credit these 

 accounts, we might infer that the enemies which the trap-door 

 spiders most dread are not such as are abroad at night. Evi- 

 dently the creatures are fearless at that time a state of mind 

 which doubtless results from their knowledge that they are com- 

 paratively free from their worst enemies. The enemies which 

 they most dread may therefore be reasonably looked for among 

 diurnal creatures, and not among those of nocturnal habits. 

 Among these foes, at least one of the most formidable and irre- 

 sistible is a diurnal insect, the female of the terrible digger wasp, 

 which I do not doubt will be found to store trap-door spiders, as 

 well as tarantulas and lycosids. There is no evidence known to 

 me that Pepsis formosa invades the tunnel of the Mygalidce, in 

 order to dig them out. Such an act is not, indeed, beyond her 

 powers ; and, reasoning from the conduct of Elis 4-notata, it is 

 highly probable. But we are not yet warranted in attributing 

 the habit to her. Some lizard or mammal that might pull open 

 the trap with its claws may be looked for as also a probable 

 enemy against which trap-door spiders erect and defend their 

 ingenious barrier. 



At all events, the spider herself is well aware of these enemies. 

 Abbe" Sauvages invariably found, when he attempted to open the 

 door of the nest of "the mason-spider" (Nemesia and Cteniza), 

 that the mother was on guard, holding down the lid of her tunnel 

 with great force. In his efforts to pull the trap-door up, the spider 

 would jerk it down, and there would be an alternate opening and 



