﻿64 



EIGHTH ANNUAL REPORT 



The Diminished Pezomachus {PezomacJius minimus Walsh) is a 

 small wingless parasite which, like the Microgaster, spins cocoons in 



[Fig. 36.] cottony floss on the back of the worm, 

 but places them close together in symme- 

 trical order. This in its turn is preyed 

 upon by a little Chalcis fly {Chalcis alhi- 



Pezomachds Mini- fronS Walsh. ) 



[Fig. 37.] 









Cocoons of 

 Pezomachus. 



All the small clear-wing parasites, with their secondary parasites, 

 were reared in 1861 by Mr. Walsh, and full descriptions will be found 

 of them in the article of his which I have already cited, and in my 

 Second Report. I reared all of them again last summer, and, in addi- 

 tion, a Microgasiei\^\i\Q\i differs from militaris in always having the 

 three basal joints of the abdomen rufous, but which is, perhaps, only 

 a variety. While about 90 per cent of the army worms are often de- 

 stroyed by the primary parasites, only about 18 per cent of these are- 

 destroyed by secondary species. 



In addition to these small parasites there are a few 

 larger, Ichneumon-flies that infest the worm. One — the Purged 

 Ophion ( Opliion purgatus Say, Fig. 38) is a honey-yellow, slender- 

 bodied, waspish insect, with a short ovipositor, the female of which, 

 according to Dr. Packard, attaches her egg, which is bean-shaped, by 

 a pedicel to the skin of the worm ; and the footless grub which 

 hatches therefrom, does not entirely leave the egg-shell, but the 

 last joints of the body remain attached thereto, while the larva 

 reaches over and gnaws into the side of the worm. I have bred 

 this same species from various cut-worms, and 

 it spins a tough, brown, silken, oblongoval 

 cocoon. 



Another species, a true Ichneumon, which 

 may be called the Army Worm Ichneumon-fly 

 {Ichneumon leucanice Fitch), was reared from 

 the worm by Dr. Fitch ; while two other spe- 

 cies are figured in Harris's Injurious Insects 

 (3rd edition p. 630). 



[Fig. 38.] 



OnilON PUKGATUS. 



REMEDIES. 



In the way of prevention it is a well established fact that burning 

 over a meadow, or prairie, or field of stubble in the Winter or in Spring 

 is an efl'ectual guard against the origin of the worm in such meadow 

 or field. Such burning necessarily destroys those eggs that may be 

 laid in the Fall of the year, and the fact that it is so effectual a pre- 

 ventive has been relied on as evidence that the eggs must be laid in 



