to some of the Insect Tribe. 51 



to illustrate the extraordinary instincts peculiar to some of 

 the insect tribes, and also afford an interesting subject to 

 the practical entomologist. 



My present communication is to give you a brief detail of 

 observations regarding the reproduction, or rather the propa- 

 gation, of a very small species of ichneumon fly (/chneumon 

 ovulorum of Linn., Platygaster ovulorum of the fam. Procto- 

 trupidae of Latreille). 



On the 28th of last month (June) I put twenty caterpillars 

 of the large cabbage butterfly (Pontia 6rassicae) into a wire 

 cage : they were mostly full-sized larvae, and continued to feed 

 on cabbage leaves placed in the cage with them. On the fol- 

 lowing day, June 29., five or six of the largest left the leaves, 

 and crawled about on the sides of the cage during the rest of the 

 day. The next morning, June 30., I found them resting on large 

 clusters of minute cocoons of an ovate form [Jig, 9. i), the 

 largest not exceeding two lines in length, and about the thick- 

 ness of a caraway seed. Each was enveloped with a fine yellow 

 silk, resembling that of the common silkworm (the pupa of Pha- 

 lae^na moYi). On these clusters the caterpillars remained the 

 whole day without moving. Fresh leaves were given to the 

 rest ; but in the course of this day they all left off feeding, 

 crawled about the cage, but underwent no other change. 

 Early the next day, July 1., I found they had, with the exception 

 of two or three, all ejected the parasitical progeny they had been 

 impregnated with, and, like the preceding caterpillars, continued 

 resting on the clusters they had formed : the remaining three 

 followed the example of the others, and the last operation of 

 these devoted caterpillars was to envelope each cluster in a 

 veil, formed of the most delicate web. Some of them executed 

 the task ; but the greater part were too feeble to complete it ; 

 and in the course of three days more, July 4., they became 

 motionless, and gradually, one after another, fell, shrivelled 

 and exhausted, to the bottom of the cage. 



The clusters of cocoons varied in their numbers ; some con- 

 tained upwards of a hundred, others not more than sixty or 

 seventy. I watched during the day to witness the change from 

 the larva to the pupa state, but in vain; the operation was 

 performed during the night, and it was only in the last two or 

 three caterpillars, in an enfeebled state, that I observed the 

 larvae of the ichneumon fly emerging from the lower side of 

 the caterpillar; but the few which came forth remained in- 

 active during the rest of the day. 



On July 12., the first-formed clusters of cocoons evinced a 

 state of maturity, and in the course of the day numbers of 

 the perfect insects came forth. Their exclusion was effected by 



E 2 



