1895.] 



253 



NOTE ON THE TRANSFORMATIONS OF A PTEROMJLUS. 

 BY THE EEV. T. A. MARSHALL, M.A., F.E.S. 



External parasites are much less numerous than internal, and offer 

 peculiarities of some interest, while their situation greatly facilitates 

 observation. I have lately had an opportunity of watching a brood 

 of them, and a record of the fact may be thought interesting, as I 



cannot find out that 

 external parasitism* 

 has ever been re- 

 markedin connection 

 with the Ghalcididee. 

 On August 17th last 

 I beat for entomolo- 

 gical purposes a bush 

 of Rosa spinosissitna 

 in my garden, from 

 which dropped a 

 Noctim. larva (fig. 1), 

 not quite full grown. 

 I saw immediately 

 that it was infested 



-r 



with thirteen parasites, adhering to various parts of its body, four in 

 a row on each side above, and five on the under-side, in groups of two 

 and three. The caterpillar was in an advanced state of marasmus, 

 the anterior half of its body being much emaciated ; it still clung to 

 leaves, but was unable to eat or to crawl. It was difficult to ascertain 

 the species, but by the help of Buckler's " Larvae," I concluded it to 

 be Mamestra brassicce, notwithstanding its unusual food-plant — for 

 hardly anything comes amiss to this somewhat pestilent caterpillar. 

 The parasites (fig. 2) were 1| mm. in length, grass-green, smooth, 

 shining, pyriform, and obtuse behind ; their cephalic extremity (for it 

 can hardly be called a head) was ])lunged into the body of the victim, 

 the posterior and blunter end remaining free ; they showed no per- 

 ceptible rudiments of eyes, palpi, or other external organs, but close 

 inspection enabled me to see a thoracic portion of their bodies, 

 followed by faint indications of segmentation along the abdomen. At 

 10 a.m. on August 18th, the caterpillar was dead, and considerably 

 shrivelled. Nevertheless, the parasites maintained their positions, 

 draining away the remaining juices of the body. On the 19th they 

 began to relax their hold, and two of them fell down upon the leaves 

 which I had placed under them. On the 20th eight more released 



