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patches of the surrounding tissues by advancing in an irregular column 
(e. g., Dendroctonus micans)-, the iuiagos when mature emerge through 
the bark by separate flight holes. 
Of the one hundred and thirty or more European species at least 
one hundred and six are known or may be assumed to possess such 
habits. 
In the Tomicini and Platypini Ave meet with divergences from the 
normal mode of life. The females of all Platypini whose habits are 
known, and of certain genera, Trypodendron, Xyleborus, etc., among 
the Tomicini bore deeply into wood, in the recesses of which the larvae 
develop. In Trypodendron the larval galleries persist as short blind 
chambers, indicating that this mode of life is an adaptation from the 
primitive subcortical habit. 
The Xylebori have gone a step farther, their larva 1 having as a rule 
abandoned the construction of galleries for themselves, and lying in 
and feeding on the contents of the mother burrows. They are further 
distinguished by the stunted and flightless condition of the males, 
which are rarer than the females, a feature not found in the less special- 
ized Trypodendra. 
The larvaB of X. ccelatus Eichh., are subcortical miners, but the pub- 
lished figures of the insect, and the description given by Eichhoff, 
Le Conte, and others indicate, as do its habits, that it should be referred 
to the genus Tomicus, where Eichhoff has placed it. The wood-boring 
habit is correlated with a different structure of the maxilhe, which are 
fringed with hairs instead of the flat spines found in phlceophagous 
species, and the two modes of life, associated as they are with struc- 
tural differences, are unlikely to occur in the same genus. The generic 
names of American Scolytids are by no means in accordance with those 
used by European coleopterists who have investigated the structure-of 
the mouth-parts, a point which widely separates the species of Gnath- 
otrichus (mater iarius, retusus, etc.) from the bark-feeding Pityophthori, 
with which they were associated by Le Conte. Fourteen European Sco- 
lytids are wood-borers, but in tropical countries the proportion of wood- 
borers to bark-feeders is much greater, and perhaps the former prepon- 
derate. 
A third habit, characteristic of certain Oryphali and Cryphalus-like 
forms (usually bark-feeders) and of Ooccotrypes is that of burrowing, 
in the manner of Anobiids into seeds, roots, and other hard substances, 
such as book-bindings. Examples are to be found in Gryphalus jalappw 
and Hypothenemtis eruditus. No European species live in this way 
except such as have been imported from time to time in their food 
materials. 
Lastly, a few Tomicini attack the softer chlorophyll-containing tis- 
sues, usually the stems, of herbaceous plants. This class of injuries is 
a modification of either of the three preceding life habits, and is of 
some interest. As yet little is known about it. 
