Qiieries and Answers. 107 



the same animal an offspring of a different species should be generated ; and 

 that one and the same creature should procreate in three different ways ; 

 which yet is manifestly the case with these caterpillars, from what I have 

 briefly related." (See Goedartii Metamorphosis, Exper. xi.) Your cor- 

 respondent, therefore, it appears, is not the first person who has been 

 amazed and puzzled by the production of parasites from lepidopterous 

 larvae, though the natural history of these insects is now understood by all 

 who have paid the least attention to the subject. See also Insect Trans- 

 formations, p. 59, CO., for information on the opinions of the earlier natu- 

 ralists. Yours, &c. — W. T. Bree. AUesley Rectory, Sept.'iQ. 1830. 



From the same invaluable contributor we have also subsequently received, 

 on the same subject, the following communication : — 



Microgdster glomcrdtus. — Sir, Towards the end of June last I observed 

 a brood of the caterpillars of Pontia brassicae (large garden white butterfly), 

 amounting 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 1st 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 Microgdster 

 glomeratus. I mention this circumstance, not at all under the idea of its 

 being any thing new or extraordinary j for I am aware, on the contrary, 

 that it is one of every-day occurrence, and that the subject, too, has 

 already been alluded to more than once in the pages of your Magazines.* 

 The object of my present notice is merely to call attention to the enor- 

 mous extent to which the destruction of Pontia brassicse is effected by the 

 Microgaster. Nine caterpillars only out of 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 very abundant 

 butterfly than we now have. In the course of a few seasons, supposing 

 no other " preventive check " to come into operation, the cabbage butter- 

 flies would increase in a kind of geometrical proportion ; our gardens 

 would soon be absolutely devoured and laid waste by the caterpillars ; and 

 it would scarcely be possible to walk abroad without being smothered by 

 the winged insects. So greatly are we indebted to this apparently con- 

 temptible little parasite (whose operations are unheeded by all but natu« 

 ralists, and of whose very existence the generality are perhaps scarcely 

 aware), for keeping down the increase of an insect which would otherwise 

 become a serious and alarming evil. 



I may observe, that, though the cabbage butterflies did not come forth 

 from the chrysalis till July 18th to 20th, the silken pupae of Microgaster 

 produced swarms of the winged insect by the 12th, ready to go forth, and 

 commence their destructive operations on fresh broods of caterpillars. — 

 W, T. Bree. Alksley Bectory, July 26. 183L 



B.S. August 9i The cabbage butterflies appeared to me to be unusually 

 abundant between London and Dartford the first week in August ; I ob- 

 served them even hovering about the stalls and green-grocers' shops in 



* See Vol. IlL p. 52., where a figure is given of Microgaster glomeratus, 

 under the name of Platygaster ovulorum ; p. 452*, where the error is cor- 

 rected by Mr. Westwood ; p. 476., Mr; Morgan's enquiry about the insect ; 

 Vol. IV. p. 95., Mr. Westwood's reply to Mr. Morgan's enquiry ,• and the 

 preceding answer to Mr. Morgan, inserted by mistake in the Gardencr^s 

 Magazine, vol. vii. p. 121. 



