302 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
trees may be killed, but the mortality of the beetles entering vigorous 
trees is so great that the infestation rapidly dies out. Concerned in 
these incipient outbreaks are such eastern species as [ps calligraphus, 
I. grandicollis, I. pini, and, more rarely, species of Pztyogenes. Spo- 
radic outbreaks of this character are very easily controlled; but, since 
most of them soon die out with only hght injury, control is hardly 
justifiable. 
The more aggressive forms, such as certain species of Dendroctonus, 
do not usually, produce heavy broods in felled or dying trees, although 
these serve as breeding places. Therefore great populations of such 
beetles are not built up in areas devastated “by lumbering, tornadoes, 
fires, or floods. 
KEYS TO BARK BEETLES 
In the following pages will be found a key by which men untrained 
in forest entomology should be able to identify the work of many of 
the eastern bark beetles, after making a field examination of the in- 
jured material. An attempt has been made to avoid the use of tech- 
nica] terms, and, insofar as possible, the key is based on the character 
of the burrows, the species of tree affected, and the part of the tree 
attacked. Insect characters are used very sparingly, and when used 
are described in nontechnical terms. 
It is hoped that such a key will prove to be useful. The ordinary 
technical key to the insects, while much easier to prepare, could be 
used only by a trained entomologist, and perhaps only by one who has 
specialized on a certain group. 
Technical keys to most of the Scolytidae and Platypodidae will be 
found in Swaine (407), Blackman ( (35 and Chamberlin.”? 
KEY TO INSECT INJURIES BY SCOLYTIDAE AND PLATYPODIDAE 
1 Entrance gallery leading directly through the bark to the surface 
of the wood, where it is elaborated into one of the v arious types 
of, barlc Burrows. ss he oe ae ee 2 
Entrance gallery proceeding through bark into the wood or even 
into.the pith 2, io -2 2b. 2. ks. ae ee ee ee 23 
2 Occurring in the inner bark of coniferous trees_________________- 3 
Occurring in the inner bark of deciduous trees_________________- 20 
3 Attacking exposed roots or basal part of trunk____________-_-_-- 4 
Attacking the main trunk or thick barked primary branches______ 6 
Attacking the medium to small branches______. Oe ee eee 1] 
Attacking the twigs: 2222 2 8° = ess) Gee ee eee 16 
Attacking ‘the:cones2 72 Aes “eee Pe ee aes ee ee eee 19 
4, Attacking fresh stumps or the bases of living pines and spruces; the 
entrance often marked by large pitch tubes: the egg gallery of 
irregular elongate type, extending downw ard from entrance__ 5 
Attacking older stumps or the bases and roots of dying trees; pre- 
ferring fermenting bark 
Hylastes spp., Hylurgops pinifex Fitch, p. 324. 
The beetles reddish brown, 5 to 9 mm. long, common in all parts of 
or 
. 
the United States____________.-Dendroctonus valens Lec., p. 319. 
The beetles nearly black, slightly smaller; Southern States, rarer 
in Norbhesst= eee Dendroctonus terebrans Oliv., p. 320. 
** CHAMBERLIN, W. J. THE BARK AND TIMBER BEETLES OF NORTH AMERICA, NORTE 
OF MEXICO. THE TAXONOMY, BIOLOGY AND CONTROL OF 575 SPECIES BELONGING TO 72 
GENERA OF THE SUPERFAMILY SCOLYTOIDEA. Oreg. State Col. Coop. Assoc. 513 pp. 
1939. [Processed.] 
