64 STATES OF INSECTS. (Lgg.) 
slight alteration, they always retain; others, and the 
greater number, assume an appearance totally different 
from that of their parents, which they acquire only after 
passing through various changes. It is to these last, which 
have chiefly engaged the attention of Entomologists, 
that the title of metamorphoses has been often restricted. 
As, however, those insects which undergo the slightest 
change of form, as spiders do, undergo some change, and 
almost all insects cast their skins several times * before 
they attain maturity, Linné and most Entomologists, till 
very recently, have regarded the whole class as under- 
going metamorphoses, and as passing through four dif- 
ferent states, viz. the Kge—the Larva—the Pupa—and 
the Imago. 
It is obvious, however, that in ovo-viviparous species 
three states of their existence only come under our cog- 
nizance, as these, being hatched in the body of the 
mother, come forth first under the form of larvae. There 
is even one tribe of insects which presents the strange 
anomaly of being born in the pupa state. This is the 
Linnean genus Hippobosca (Pupipara Latr.), to which 
our forest-fly belongs, the females of which lay bodies 
so much resembling eggs, that they were long consi- 
dered as such until their true nature was ascertained by 
Reaumur (most of whose observations were confirmed 
by De Geer), who, from their size, which nearly equals 
that of the parent fly—from their slight motion when 
first extruded—from spiraculiform points which run down 
each side of them—and lastly, from their producing not 
4 I say almost all insects, because the larvee of Hymenoptera and 
Diptera are supposed not to undergo this change. NV. Dict. d’ Hist. 
Nat, xx. 365. 
