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“patches of the surrounding tissues by advancing in an irregular column 
(e. g., Dendroctonus micans); the imagos 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 we meet with divergences from the 
normal mode of life. The females of all Platypini whose habits are 
known, and of certain genera, Trypodendron, Xyleborus, ete., among 
the Tomicini bore deeply into wood, in the recesses of which the larvie 
develop. In Trypodendron the larval galleries persist as short blind 
ehambers, indicating that this mode of life is an adaptation from the 
primitive subcortical habit. 
_ The Xylebori have gone a step farther, their larve 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 larvee of XY. celatus Kichh., are subcortical miners, but the pub- 
lished figures of the insect, and the description given by Hichhoff, 
Le Conte, and others indicate, as do its habits, thatitshould be referred 
to the genus Tomicus, where Hichhoff has placed it. The wood-boring 
abit is correlated with a different structure of the maxille, which are 
fringed with hairs instead of the flat spines found in phlwophagous 
species, and the two modes of lite, associated as they are with struc- 
tural differences, are unlikely to occur in the same genus. The generic 
james of American Scolytids are by no means in accordance with those 
ased by European coleopterists who have investigated the structure-of 
the mouth-parts, a point which widely Separates the species of Gnath- 
otrichus (materiarius, retusus, etc.) from the bark-feeding Pityophthori, 
with which they were associated by LeConte. Fourteen European Sco- 
ids are wood-borers, but in tropical countries the proportion of wood- 
borers to bark-feeders is much greater, and perhaps the former prepon- 
lerate. . 
_ A third habit, characteristic of certain Cryphali and Cryphalus-like 
orms (usually bark-feeders) and of Coccutrypes is that of burrowing, 
nthe manner of Anobiids into seeds, roots, and other hard substances, 
uch as book-bindings. Examples are to be found in Cryphalus jalappee 
nd Hypothenemus eruditus. No European species live in this way 
xcept such as have been imported from time to time in their food 
naterials. 
Lastly, a few Tomicini attack the softer chlorophyll-containing tis- 
ues, usually the stems, of herbaceous plants. This class of injuries is 
modification of either of the three preceding life habits, and is of 
ome interest. As yet little is known about it. 
