Sept., '05] ENTOMOLOGICAL NEWS. 233 



An Enemy of the Trap Door Spider. 



BY ANSTRUTHER DAVIDSON, M. D., L,os Angeles, Cal. 



About a dozen years ago I was much interested in the habits 

 and ways of spiders, but the difficulties experienced in deter- 

 mining the various species soon discouraged me, and I ceased 

 to give them special attention. The habits of Cteni-.a calif or- 

 nica, our common trap door spider, is still a perennial source of 

 interest, and in my observations of my pet colony on the edge 

 of a ravine in East L/os Angeles, I observed not a few nests 

 which showed a perforation in the door. These all on opening 

 disclosed the empty cocoon of a wasp. I zealously set to work 

 to find some fresh cocoons. It seemed that I would require 

 to dig up the whole colony on the chance of finding a few, but 

 investigation in that autumn showed that the trap door which 

 had been so carefully guarded in the spring and early summer 

 was now tightly sealed down, either by silk alone, or by silk 

 and earth, as is their method of building. The spider itself had 

 retired to the bottom of the cell in what might be considered 

 a "state of hibernation. As no spider with a sealed door could 

 possibly be attacked by any wasp, it was only necessary to 

 test all the traps and examine those found unsealed. Some of 

 those contained the remains of spiders, a few were empty, and 

 four contained fresh cocoons, two of which were successfully 

 hatched out and determined by Prof. Coquiliett as Parafiont- 

 pilns planatus Fox. 



I have never seen this wasp hovering near the trap door 

 spider's retreat, so I cannot state definitely by what method the 

 wasp attacks the spider. Two possible methods may be con- 

 sidered. The wasp may attack the spider when it leaves its 

 nest in the twilight, sting, and paralyze it, carry it to the 

 spider's nest, lift the trap door and drop it in. Or the wasp 

 taking advantage of an unwary moment opens the door, drops 

 in, attacks and overcomes the spider in its retreat. After the 

 battle she deposits her egg on the spider and departs. 



Of the two possible methods the latter seems to me the more 

 probable, as it would not be easy if it were even possible for 

 the wasp to hold up the lid, and at the same time drag such a 



