164 ENTOMOLOGY 
involving the eruciferm condition, Packard finds in the neu- 
ropterous genus Mantispa (Fig. 211), the first larva of which 
is truly campodea-form and active. Beginning a sedentary 
life, however, in the egg-sac of a spider, it loses the use of its 
legs and the antennze become partly aborted, before the first 
moult. In Packard’s words, “ Owing to this change of hab- 
its and surroundings from those of its active ancestors, it 
changes its form, and the fully grown larva becomes cylin- 
drical, with small slender legs, and, owing to the partial disuse 
of its jaws, acquires a small, round head.” Meloide (Tig. 
217) afford other excellent examples of the transition from 
the thysanuriform to the eruciform condition’ during the life 
of the individual. 
Thysanuriform characters become gradually suppressed in 
favor of the eruciform, until, in most of the highly developed 
orders (Mecoptera, Trichoptera, Lepidoptera, Diptera, Si- 
phonaptera and Hymenoptera), they cease to appear, except 
for a few embryonic traces—an illustration of the principle of 
“acceleration in development.” 
Growth.—The larval period is pre-eminently one of growth. 
In Heterometabola, growth is continuous during the nymphal 
stage, but in Holometabola this important function becomes 
relegated to the larval stage, and pupal development takes 
place at the expense of a reserve supply of food accumulated 
by the larva. 
The rapidity of larval growth is remarkable. Trouvelot 
found that the caterpillar of Telea polyphemus attains in 56 
days 4,140 times its original weight (1/20 grain), and has 
eaten an amount of food 86,000 times its primitive weight. 
Other larve exceed even these figures; thus the maggot of a 
common flesh fly attains 200 times its original weight in 24 
hours. 
Ecdysis.—The exoskeleton, unfitted for accommodating 
itself to the growth of the insect, is periodically shed, and 
along with it go not only such integumentary structures as 
hairs and scales, but also the chitinous lining, or intima, of 
