INSECT ENEMIES OF EASTERN FORESTS 153 
THE BEETLES 
Orpver COLEOPTERA 28 
_ The beetles are distinguished from other insects by having a com- 
plete metamorphosis, biting mouth parts, and hardened forewings, or 
elytra, which cover the folded and membranous hind, or second pair 
of wings, when the latter are present. 
The larvae of these forms cannot be thus briefly characterized to 
set them off-from those of other insects. The modification and com- 
plexity of form which occurs in this order is extremely varied, dupli- 
cating the aquatic adaptation of the Neuroptera, the leaf-feeding and 
wood-boring habits of the Lepidoptera, and the parasitic habits of 
the Hymenoptera, each with paralleled modifications of structure. 
Consequently, for present purposes no attempt will be made to give 
a combination of characters that will define the larvae of this order 
and set them off from the others. 
As previously stated, the diversity of habits in this order is ex- 
tremely marked. Whole families are fitted for aquatic life, both as 
larvae and adults; some are active predaceous swimmers: others live 
sedentary lives under stones and are provided either with gills or with 
special mechanisms to store air; some families are primarily parasitic 
with a complicated metamorphosis and highly modified adaptation to 
varied existences in their development; many are active predators or 
scavengers on the surface of the ground; and many of those with 
which we are chiefly concerned are phytophagous. Of these plant- 
feeding forms certain modifications are found which fit the larvae or 
the adults to feed on different portions of the plant—roots, stem, twigs, 
buds, leaves, or seeds. Some attack only living tissue, others recently 
dead or dying plant tissue, and again there are those that feed only 
on decaying vegetation or the fungi associated with decay. 
The beetles are probably the most important order of forest insects 
from an economic standpoint. The widespread destruction of mature 
timber caused by the bark beetles, and the injury to forest products 
from the attack of roundheaded and flatheaded borers and powder- 
post beetles are notable instances of their destructive powers. 
Many adults of this order cause extensive defoliation, other beetles 
kill living timber by introducing blue stain fungi, but the larval stage 
is generally the most destructive. For this reason it seems desirable 
in a discussion of this kind to give emphasis to the description and 
recognition of the larval stages. At present the larvae are very inade- 
quately treated in economic literature. For simplicity and practi- 
cability the keys used to distinguish the coleopterous larvae combine 
anatomical and biological characters. Those characters mentioned in 
the keys are frequently not repeated under the family or species de- 
scriptions and must be taken into consideration for an adequate 
characterization of the forms. For more extended treatment of this 
order the reader is referred to the following works: Blatchley (47), 
Boving and Craighead (52), Bradley (53), Leng (273), and Leng and 
Mutchler, (274, 275). 
8 The information on this order has been compiled by the following authorities: 
The Lamellicornia by L. E. Yeager; the Chrysomelidae and Rhynchophora by 
H. J. MacAloney (except larval discussion) ; the Tenebrionidae and a few related 
forms by R. A. St. George; the Scolytidae and Platypodidae by M. W. Blackman ; 
the Buprestidae by J. N. Knull; and the remainder by F. C. Craighead. 
