24 EN TOMOLOGY 
metamorphosis, which appears in Neuroptera and attains its 
maximum development in Diptera and Hymenoptera. 
With Neuroptera the eruciform type of larva appears, as a 
derivative of the earlier thysanuriform type. The larva of 
Mantispa, as Packard has shown, actually passes, during its 
individual development, from the primary, thysanuriform 
stage to the secondary, eruciform condition. 
Mecoptera form an isolated order, though their caterpillar- 
like larvee, with eleven or twelve pairs of legs, suggest affini- 
ties with Lepidoptera and, more remotely, with the tenthred- 
inid Hymenoptera. 
Trichoptera, while much like Mecoptera in structure and 
metamorphosis, are undoubtedly closely related to Lepidop- 
tera; in view of the extensive and deep-seated resemblances 
between caddis flies and the most generalized moths ( Microp- 
terygide) there is little doubt that Trichoptera and Lepi- 
doptera originated from the same stock. 
The origin of the coherent group Coleoptera 1s by no means 
clear, although thysanuriform larve occur frequently in this 
order. Packard suggests that both beetles and earwigs arose 
from some thysanuroid form or that the primitive coleopterous 
larva sprang from some metabolous neuropteroid form. In 
any linear arrangement of the orders the position of Coleop- 
tera is largely arbitrary, and here the order is intruded between 
Lepidoptera and Diptera simply for want of a more satisfac- 
tory place. 
Lepidoptera, Trichoptera and Mecoptera are probably 
branches from one stem. Lepidoptera, Diptera and Hymen- 
optera are regarded by Packard as having had a common 
origin from metabolic Neuroptera. 
Among Diptera, such larve as those of Culicidze are com- 
paratively primitive, according to Packard, and larvzee of Mus- 
cide are secondary, or adaptive, forms. 
Siphonaptera used to be regarded as Diptera and are prob- 
ably an offshoot from the dipteran stem. 
The most primitive hymenopterous larvze are those of the 
