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Psyche 
[April 
but only by clearly primitive nematocerous types (except for one 
typical Xylophagid). We may therefore safely conclude that 
this order had its origin after the Permian in the Liassic. 
With these facts in mind, as gleaned from the paleontolo- 
gical data so far accumulated, we may inquire more in detail- 
concerning the occurrence and distribution of xylophagous habits 
in these several orders. 
In the Lepidoptera there are several very generalized fam- 
ilies which form the suborder Homoneura. Of these the small 
but widely distributed family Hepialidse includes large moths 
most of which develop in burrows that they excavate in wood, 
while others are subterranean and feed upon the roots of trees. 
Although not entirely lignivorous, it is interesting to note that 
the most primitive of all families belonging to the Homoneura, 
the Micropterygidse includes species that mine in the leaves of 
trees as well as forms that feed upon more primitive plants such 
as mosses and liverworts. 
Another primitive family, the Cossidse, includes large moths 
which are xylophagous as larvae, and as typified by members like 
the Leopard Moth (Zeuzera) and Carpenter Moth (Prionoxys- 
tus) are notoriously destructive to certain deciduous trees. Like- 
wise the related family Sesiidae (Aegeriidse) restrict their diet to 
the wood of trees except in rare instances where a few species 
have become secondarily associated with herbaceous plants. 
These several families are all internal feeders and true wood- 
borers, but even in the case of one family which feeds on foliage, 
the leaf-rolling Tortricidae, the selection of trees rather than 
herbaceous plants is very marked. Another series which ex- 
hibits the same predilection for trees is the enormous family 
Geometridse. These are however not so important from the 
present standpoint, for although quite generalized they are by 
no means so primitive as the other families mentioned. 
Among the Hymenoptera the case is still clearer for the 
most primitive groups not only of phytophagous types but of 
parasitic ones as well are definitely associated with the woody 
flora. There is some ground for a difference of opinion in select- 
ing the most primitive living type of Hymenoptera and also in 
indicating the probably phylogeny of the lower groups. On the 
