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Order COLEOPTERA 
Beetles 
The beetles comprise the largest order of insects. Over a quarter 
of a million species have been described, and over 26,000 of this 
number occur in the United States. They can be distinguished 
from all other insects, except the earwigs, by the structure of the 
forewings, these being horny “wing covers” or elytra which meet 
in a straight line along the middle of the back (152). They cover 
the membranous hindwings when the latter are present. Beetle 
larvae vary considerably in form in different families. The ma- 
jority are campodeiform or scarabaeiform, but some are platy- 
form, some are elateriform, and a few are vermiform. All beetles 
have complete metamorphosis, and all have chewing mouth parts. 
The life cycle varies greatly in length, from 10 or more genera- 
tions per year to one generation in many years. 
Beetle larvae and adults present a wide range of habits. 
Some species are aquatic, but the majority are terrestrial. Some 
feed on vegetable matter; others on animal matter. Many are 
phytophagous, many are predaceous, some are scavengers, some 
feed on mold or fungi, and a few are parasitic. 
Many species of the phytophagous beetles are external feeders 
on the foliage, and many others feed under the bark. Some feed 
in the wood or fruit, on parts of blossoms, as miners in leaves, or 
on the roots of their hosts. Some of the predaceous species feed 
both as larvae and adults on free-feeding lepidopterous larvae and 
various sucking insects; others feed on various insects in the leaf 
litter and under logs, or on the immature stages of bark beetles 
and wood borers in their burrows in wood. A few of the parasitic 
species feed on the egg masses of grasshoppers or in the nests of 
bees. 
The order Coleoptera contains many of the most destructive 
forest insects. The adults of many leaf-eating species cause exten- 
sive defoliation and damage. Many others kill valuable timber or 
shade trees by introducing blue-staining fungi or other lethal 
pathogens as they bore into their hosts. The larvae are generally 
most destructive, however. For example, enormous losses of stand- 
ing timber are caused each year by phloem-feeding larvae; severe 
losses in timber degrade and to forest products are caused by the 
larvae of various woodboring species. Young trees in nurseries 
and plantations as well as natural reproduction are severely dam- 
aged or destroyed by the larvae of other species. 
For more extended treatment of the Coleoptera, the reader is 
referred to the following works: Blatchley (81), Boving and 
Craighead (91), Bradley (94), Leng (461), and Leng and 
Mutchler (452, 453). Dillon & Dillon published a manual of 
species occurring in eastern North America (193). 
Key to the Families of More Important Beetle Larvae 
1. Legs apparently 6-jointed, the 5th bearing 1 or 2 distinct 
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Legs either 5- jointed with. tarsus and claw fused into 
a single claw ail terminal oe or less than 5- 
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