Packard.] 
498 
[Feb. 19, 
Endromidce. — The single species is arboreal. 
Psychidce. — The two species, whose larval habits were known, 
feed on trees and shrubs. 
Cochliopodidce. — The two species feed on trees. 
Saturniidce. — The single British species feeds on the heather, a 
shrubby plant. 
Lasiocampidce. — Of eleven species, five feed on trees, the others 
on shrubs and herbs. 
Noctuo-bombyces. — All the British species are reported as “living 
on trees and shrubs quite exposed.” 
Bombycidce. — All the species of Acronycta live on trees and 
shrubs. 
Influence of a change from low- to high-feeding plants, i. e.,from 
living on an herbaceous to an arboreal station. — It appears, then, 
that the more typical Bombyces, such as the Ceratocampidse, Hem- 
ileucini, Attaci, Notodontians, Cochlidise, and Liparidse are arbo- 
real in their station, their bodies being variously protected by spines, 
spinulated tubercles, hairs or tufts. The group is indeed particu- 
larly distinguished for the manifold modifications undergone by 
what are morphologically setse, and it is an interesting inquiry 
whether the great development of these spines and hairs may not 
have originally resulted from a change in environment, i. e., from 
low-feeding to high-feeding or arboreal habits. 
It may be objected that the setse and spines were originally due 
to the stimulus arising from the attacks of parasitic insects, such 
as ichneumons and Tachinse, or that, as hairy caterpillars are not 
usually devoured by birds, these hairs and spines have originated 
through natural selection, and are danger-signals, indicating to 
birds that the wearers of such hirsute and bristling armature are 
inedible. But while the final purpose or ultimate use of such an 
armature may serve the useful purpose of protection, and while 
natural selection may have been the leading secondary factor in 
the preservation of varietal and specific forms of hairy and spiny 
caterpillars, this does not satisfactorily account for the initial 
causes of the growth of tubercles, spines, etc. 
If spines and hairs form hedge-like guards against the attacks 
of parasitic insects, why are they not developed as well in the 
great multitude of low-feeders as in the less numerous high-feed- 
ers? Every one knows how efficacious any hairs or bristles are' in 
deterring ichneumons and Tachinse from ovipositing on caterpil- 
