DEVELOPMENT 163 
Eruciform Larvz.—The prevalent type of larva among 
holometabclous insects is the eruciform (Fig. 210, E-/), illus- 
trated by a caterpillar or a maggot. Here the body is cylin- 
drical and often fleshy; the integument weak; the legs, anten- 
nz, cerci, and mouth parts reduced, often to disappearance; 
the habits sedentary and the sense organs correspondingly re- 
duced. These characteristics are interpreted as being results of 
partial or entire disuse, the amount of reduction being propor- 
tional to the degree of inactivity. Extreme reduction is seen 
in the maggots of parasitic and such other Diptera as, secur- 
ing their food with almost no exertion, are simple in form, 
thin-skinned, legless, with only a mere vestige of a head and 
with sensory powers of but the simplest kind. 
Transitional Forms.—The eruciform is clearly derived 
from the thysanuriform type, as Brauer and Packard have 
shown, the continuity between the two types being established 
by means of a complete series of intermediate stages. The 
CMI: WA > 
y SF om, Sy Ley 
ii —— TE 
Ry 
Mantispa. <A, larva at hatching—thysanuriform,; B, same larva just before first 
moult—now becoming eruciform. C, imago, the wings omitted; D, winged imago, 
slightly enlarged.—A and B after Braver; C and D after Emerton, from Packard’s 
Text-Book of Entomology, by permission of the Macmillan Co. 
beginning of the eruciform type is found in Neuroptera, where 
the campodeoid sialid larva assumes a quiescent pupal condi- 
tion. The key to the origin of the complete metamorphosis, 
