184 LARGE CABBAGE BUTTERFLY. 



the Ichneumon globatus, which had totally consumed 

 their intestines. * I do not, however, give this as an 

 average of the numbers destroyed by their means. 

 The following interesting observations by the Rev. 

 Mr Bree, which are of a recent date, may serve to 

 shew the more probable numbers which suffer by this 

 means : " Towards the end of June last,f I observed 

 a brood of the caterpillars of Pontia brassicce, amount- 

 ing in number to twenty-four, feeding on the cabbages 

 in my garden. I placed them in confinement ; and, 

 as they were nearly full grown, they soon commenced 

 preparing for their transformations. By the first of 

 July, nine out of the twenty-four had turned to the 

 chrysalis state, and the remaining fifteen produced 

 the silken clusters of pupae of Microgaster glomoratus. 

 I mention this circumstance, not at all under the idea 

 of its being any thing new or extraordinary ; for I 

 am aware, on the contrary, that it is one of every -day 

 occurrence, and my object is to arrest the attention 

 to the enormous extent to which the destruction of 

 Pontia brassicfs is effected by the Microgaster. Nine 

 caterpillars only, out of the twenty-four, came to 

 maturity as butterflies ; the remaining fifteen (i. e. 

 nearly two thirds,) were destroyed by the parasite. 

 Now, if the present instance is to be taken as a fair 

 average example of what usually occurs, (and I see 

 no reason why it may not,) we should have had this 

 season, were it not for the ravages committed by the 

 Microgaster, almost two-thirds more of this already 



* Reaumur, ii. p. 419. f 1830. 



