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604
COLLEGE ENTOMOLOGY
parts. Some species also attack unhealthy, recent1y ki11ed, or old wood while
others feed only in the living tissues. The heartwood, the growing areas between
the wood and bark, and the bark are invaded.
The ambrosia beetles (often separated as the family PLATYPODIDiE) living
in dead wood cultivate fungi to feed their young while in other species woodrotting
fungi assist in the utilization of the wood for food. The species are
monogamous or polygamous;
sometimes both sexes aid in
constructing the primary gallery
and sometimes the work is done
only by the fertilized females.
The minute white eggs are scattered
along the primary galleries,
and the larvre make new
tunnels either transverse or
parallel to them. In the ambrosia
beetles there are indications
of a social organization
built around the cultivation of
fungi for food. Often the burrows
form definite patterns
which are characteristic of the
individual species and aid in
their identification.
While many species attack
deciduous and broad-leaved
trees and shrubs, the greatest
damage is done to the coniferous
forests of the world. In the
United States the annual losses
in destruction of timber amounts
to $62,000,000 annually (Doane
FIG. 210. Galleries of the cypress barkbeetle,
PhlmosilZus cupressus Hopkins, in the outer sapwood
of the Monterey cypress.
et al., 1936).
The family is a fairly large
one that includes about 2,000
species. It is dominant in the
temperate regions and is noticeably. scarce in Africa. In size the adults vary
from the minute Crypturgus pusillus Gyllenhal of Europe and C. atomus
LeConte of North America which are about 1 mm. long to Dendrocionus
micans Kugelan, one of the commonest European species, and the red
turpentine beetle, D. valens Lee., one of the most widely distributed American
species, which vary from 5-9 mm. in length.
Among the most important genera are the following: Xyleborus Eichhoff with
239 spp. is not only the largest, but also the most widely distributed cosmopolitan
genus. Scolytus Geoffroy, 72 spp., is also cosmopolitan while Cryphalus