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well known six hooks. The tail moves up and down, and is of 
but little assistance in its efforts to change its place. Singularly 
enough, the nervous, vascular, and respiratory systems (trachezx) 
are wanting, and the alimentary canal is a blind sac, remaining in 
an indifferent, or unorganized state. How long it remains in this 
stage could not be ascertained. E 
The second larval stage (Fig. 18; œ, esophagus ; ng, supraœso- 
phageal ganglion ; n, nervous cord ; ga, and g, genital organs; ms, 
bands of muscles) is attained by means 
of a moult, as usual in the metamor- 
phoses of insects. . With the change of 
skin the larva entirely changes its form. 
So-called hypodermic cells are devel- 
oped. The singular tail is dropped, 
the segments of the body disappear, 
and the body grows oval, while within 
begins a series of remarkable changes, 
like the ordinary development of the 
embryo of most other insects within the 
egg. The cells of the hypodermis mul- 
tiply greatly, and lie one above the 
other in numerous layers. They give 
rise to a special primitive organ closely 
resembling the “ primitive band” of all 
insect embryos. The alimentary canal 
is made anew, and the nervous and 
vascular systems now appear, but the 
trache are not yet formed. It re- 
mains in this state for a much longer 
period than in the previous stage. 
The third larval form only a few live — 
to reach. This is of the usual long, 
oval form of the larvæ of ichneumons, and the body has thirteen: 
segments exclusive of the head. The muscular system has greatly 
developed and the larva is much more lively in its motions than _ 
before. The new organs that develop are the air tubes and fat 
bodies. The “imaginal dises” or rudimentary portions destined 
to develop and form the skin of the adult, or imago, arise in 
i the pupa state, which resembles that of other ichneumons. These 
dises are only engaged, in Platygaster, in building up the rudi- 
Fig. 17. 
First larva of Platygaster. 
