REVIEWS. 43 
ichneumon egg-parasites of the hymenopterous family Proctotry- 
pide, of which the Platygaster of the Canker worm (Fig. 14) and 
Platygaster error Fitch (Fig. 15, copied from the ‘Guide to the’ 
Study of Insects”) are familiar examples. It has been generally 
supposed that the larve of these egg-parasites were little foot- 
Fig. 14. less, white maggots, like the young of other ich- 
VS neumon flies. In the valuable and well illustrated 
memoir before us, however, the author, a Russian 
* professor who pursued these studies under the direc- 
Egg-parasite ot ON OF the distinguished Leuckart of Giessen, shows 
Canker Worm. that the insects pass through a series of remarkable 
changes before assuming the final, and more normal larval state, 
the series of changes indicating a succession of metamorphoses, 
comparable, as Ganin says, to the hyper-metamorphosis of Meloé 
and Sitaris. | 
The earliest stages of the embryo of Platygaster were observed 
in the youngest specimens of Cecidomyia larvæ, or dipterous gall 
maggots, which live exposed on 
young willow leaves. The female 
sometimes lays from twelve to fif- 
teen eggs in the body of the larval 
Cecidomyia, though usually not so ¥ 
many. When they are numerous 
they are not all laid at one time, 
as the embryos are found to be in 
different stages of development. 
Usually only one out of the whole 
number of embryos leaves the bod 
of its host as a fly. The eggs are generally laid in the masses of 
cells composing the “fatty body,” and in the interior of (or be- 
neath, im innern) the supracesophageal ganglion of the Cecidomyia 
larva. Not one species only, but sometimes three species of Platy- ` 
gaster oviposited in the body of a single gall-fly maggot. These 
differed from each other in the size of the egg, and very strik- 
ingly in the form of their first larval stages. One of these Platy- 
gasters lays its eggs (from one to six) almost exclusively in the 
intestines of the gall maggot. The eggs of the other species of 
Platygaster are usually found in the body-cavity of their host. It 
is sometimes impossible to find a Cecidomyia larva which is not 
infested by these parasites. The death of the host oceurs shortly 
Platygaster error. 
