310 Observations on Insects affecting t/te Turnip Crops. 



rally dies close to liis murderers. Even these parasites are subject 

 to the attacks of a beautiful little fly, called Diplolfjns (Pter- 

 omalus ?) Microgastri of Bouchc,* the maggots of which live in 

 the pupae of Micrcgaster glomeratus, three or four together, and 

 the silken cases which are inhabited by these parasites are paler 

 than the healthy ones : thus one little animal lives upon another ; 

 so that the laughable lines of the facetious poet are partly verified : 



" That fleas have little fleas to bite 'em, 

 And so go on ad infinitum^ 



Persons who are ignorant of the wonderful operations of nature, 

 often mistake these yellow cocoons formed by the maggots for the 

 eggs of the caterpillars, and accordingly destroy them, although 

 they ought rather to be preserved ; and others, on opening a 

 caterpillar of the White Cabbage-Butterfly and finding it full of 

 little maggots, have supposed they were the young of it. Such 

 errors are the offspring of ignorance, and contrary to the laws 

 which regulate the generation of these animals ; and I trust that 

 these careful investigations will meet with the attention of agricul • 

 turists, that they may take a correct view of these subjects, which 

 are at once interesting and of absolute importance to mankind. 



There is also a large Ichneumon-Hy, the larva of which lives 

 singly in the chrysalis of P. Brassicce, and changes into a white 

 pupa inside, without forming any case ; the fly hatches in two or 

 three weeks; it is likewise Hymenopterous, and of the Family 

 IcuNEUMONiDJ-: : it has been named 



3. Pimpla instigator, Fah.; f it is black and thickly punctured ; 

 the two slender horns are not so long as the body, and composed 

 of numerous oblong joints ; the elliptical abdomen is only slightly 

 narrowed at the base; the thighs, shanks, and feet are bright 

 fulvous, excepting the hinder feet, which are brown or black ; 

 the four wings are dull-yellowish, but iridescent, the stigma and 

 nervures brown, the areolet is rhomboidal ; the female has a stout 

 ovipositor projecting beyond the apex, and is nearly half as long 

 as the abdomen : the male is often J an inch long, the wings ex- 

 panding more than | of an inch, and the female is considerably 

 larger. This powerful insect likewise infests the caterpillars of 

 many moths, and emits a most offensive scent when touched : I 

 have frequently seen the females running over fruit-trees, in- 

 vestigating every leaf and crevice to find a proper object to receive 

 their eggs : they are met with from Midsummer to Michaelmas. 



There are other parasites which destroy the chrysalides ; and 

 one of the most essential of these is a minute brilliant fly, which 

 deposits its eggs upon the outside of the chrysalis of the Butterfly, 



* Naturgeschichte der Insecten, p. 168. 

 t Curtis's Brit. Ent, fol. and pi. 214; and Guide, Gen. 515, No. 103. 



