﻿1869.] 155 



(about half), the wasp meets with some accident, and her burrow 

 remains uncompleted, the cell last constructed being thus only pro- 

 tected by the wall of clay that was to serve as a party wall between it 

 and the succeeding one, had the wasp lived to complete her work. Such 

 slightly protected cells are those chosen by G. bidentata for her ovi- 

 position. I once found satisfactory evidence of C. bidentata having 

 burrowed through half-an-inch of the clay stopping placed by the wasp 

 over one of these cells. The parasite was in the burrow, covered with 

 the dust brought down into it by her excavation to form an entrance, — 

 a passage too small for the wasp to enter, but just large enough for 

 herself; and in the cell thus reached by her were to be seen her eggs 

 freshly deposited. On another occasion, a G. lidentata alighted on a 

 spot I was examining, and where I had partially exposed some cocoons 

 of O. spinipes ; she commenced to carefully investigate them with her 

 antennae, and now and then to scratch away some earth partly covering 

 them; she did not, however, deposit any egg, possibly because the 

 inmates of the cocoons were not in proper condition. 



When a cocoon contains eggs of G. bidentata, there is often to be 

 found, at its upper end, a minute aperture, through which the ovi- 

 positor of the Ghrysis has been thrust ; at other times, this] aperture 

 is wanting, simply, I believe, because the larva of 0. spinipes had not 

 done spinning her cocoon when the Ghrysis deposited her eggs within 

 it. There is nearly always a small spot outside on the yellow silken 

 top of the cocoon, as if the Ghrysis had attacked it first with her 

 jaws ; and those containing G. bidentata may be selected by this mark 

 from a number of cocoons of the Odynerus. One of the most remark- 

 able points of their history is, that G. bidentata does not deposit one 

 egg only in the cocoon of the Odynerus, but actually drops m. from six 

 to ten eggs. These do not appear to be placed in any particular posi- 

 tion, but simply fall on the enclosed larva ; and the excess in number 

 may obviate the destruction caused by the latter, especially when its 

 movements are still active, before the completion of its spinning opera- 

 tions. In the instance above noted, where I found G. bidentata in the 

 burrow of 0. spinipes, the cocoon of the latter contained five eggs in 

 good condition. The wasp larva had ceased to spin, but had not yet 

 shrunk to those smaller dimensions which it rapidly assumes soon after 

 that period. In various other instances, I found two healthy eggs of 

 G. bidentata, but often only one, the shrivelled cases of from four to 

 eight others being found with the healthy eggs. I never found any 

 evidence of the hatching of two eggs of G. bidentata in the same cell ; 



