THE BIOLOGY OF THE MUD-DAUBING WASPS 35 



could not gain their freedom by way of the under side, which 

 was partly open; the table merely replaced the board wall upon 

 which it had been built. Fourteen wasps escaped in the normal 

 way from the top layer and the periphery of the lower layer. 

 Seven adults in the central cells could not escape, but each one 

 bored through the wall and entered the adjacent cell, where 

 they were found dead. They followed no special direction in 

 boring out of these lower cells; one had bored through the front 

 wall, and the other borings were equally divided on either side. 

 In one such dungeon three dead prisoners were found, the 

 original inmate of the cell and the neighbor from either side. 

 Had each one of these seven mature insects had the instinctive 

 courage or energy to push on through one more wall, all would 

 have escaped. In another nest we found where this same in- 

 ability had brought death to one insect, the only one in the nest 

 that was so situated that its exit led into another cell. In a 

 third nest the same was true for two insects. We cannot call 

 this defective instinct, but only simple instinct, for in the insects' 

 normal experience they should have but one wall to penetrate 

 in order to gain their freedom. 



One would like to say at least that it is wonderful that the 

 emerging wasp knows how to direct its exit towards the ligr^t, 

 but even this is not always the case. I have another record 

 of an eight-celled, one-story nest in which three individuals 

 had bored through the side-wall into their neighbor's cell and 

 died there, instead of breaking through their own roof to free- 

 dom. So even this instinct of working out toward the light 

 is sometimes defective. 



PARASITES AND LESEES 



Often one finds other species occupying the nests or preying 

 upon the wasps at home. Among these are: 



Parasites 



Cuckoo-bees, Trichrysis tridens 8 Lep. and T. parvula* Fab. 

 Dipteron, Toxophora americana Guerin. 

 Dipteron, Spogostylum fur O. S. 

 Dipteron, Argyromoeba obsoletum Loew. 

 Hymenopteron, Melittobia. 



8 Identified by Mr. S. A. Rohwer. 



