DEVELOPMENT OF INSECTS. 
331 
appendages bud out from the under side of the primitive 
band, and antenne, jaws, legs, ovipositor (or sting), and the 
abdominal feet of caterpillars are at 
ternal organs, the ner- 
vous system first origi- 
nates; the alimentary 
Fig. 294.-Embryo of Sphinx te formed 5 
much more advanced. f, heart; and at about this time 
g, ganglion; i, intestine; m G z 
rudimentary muscular bands run- the stigmata and air- 
Deglaning of a tiackes We dea tubes arise as invagina- 
sek Kowakevcne, ee *%3, 295 tions of the outer germ- 
layer. The development 
of the salivary glands precedes that of the uri- 
nary tubes, which, with the genital glands, are 
originally offshoots of the primitive digestive 
tract. Finally the heart is formed. 
When the insect hatches, it either cuts its way 
through the egg-shell by a temporary egg-cut- 
ter, as in the flea, or the expansion of the 
head and thorax and the convulsive movements 
of the body, as in the grasshopper, burst the 
shell asunder. The serous membrane is left in 
the shell, but in the case of grasshoppers the 
larva on hatching is still enveloped in the am- 
nion. This is soon cast as a thin pellicle. 
The principal change from the larval to the 
adult locust or grasshopper is the acquisition of 
wings. In such insects, then, as the Orthoptera 
and Hemiptera, in which the adults differ from 
the newly hatched larva mainly in the posses- 
sion of wings, metamorphosis is said to be in- 
first all alike. Soon the appendages 
begin to assume the form seen in 
the larva, and just before the insect 
hatches the last steps in the elabora- 
tion of the larval form are taken. 
As to the development of the in- 
ic iC IC 
aiaN oles 
CIC} 
Z(CACt 
@ 
ou Ie 
1c or 
Fig. 295. 
Primitive 
band or germ 
of a Sphinx 
moth, with the 
segments | in- 
dicated, ‘and 
their rndimen- 
tary append- 
“ages. c¢, upper 
lip 5 az. anten- 
ne ; md, man- 
dibles; ma, 
ma’, first and. 
secund maxil, 
le; Z, i, 
legs ; al, abde 
minal legs. 
complete. In the'beetle, butterfly, or bee, the metamorphosis. 
ss complete ; the caterpillar, for example, is a biting insect, 
