6 BULLETIN 426, U. &. DEPARTMENT OF AGRICULTURE. 
been found on mature green trees. Polyporus volvatus is common on 
dead trees. The damage done by the former is minor, and that 
wrought by the latter is of no importance. 
INSECTS. 1! 
Insecis are responsible for the destruction of large quantities of 
merchantable sugar pine timber. In the northern portion of the 
tree’s range bark beetles of the genus Dendroctonus are very destruc- 
tive; in the southern portions their work is supplemented by that of 
the flat-head beetles of the family Buprestide. The annual loss of 
sugar-pine timber from beetles is roughly estimated at not less than 
one-half of 1 per cent of the merchantable stand. In certain localities 
epidemics of insects have resulted in the loss of from 5 to 10 per cent. 
While the roots, limbs, twigs, foliage, cones, and seed of this tree 
all have insect enemies a tree is never known to have been destroyed 
except by those which attack the trunk. The mountain pine beetle 
(Dendroctonus monticole, Hopk.) is by far the most serious enemy. 
The adult beetles bore through the cork bark and deposit their eggs 
in the living inner bark, which is an important part of the circulatory 
system of the tree. Upon hatching, the larve or grubs completely 
girdle the tree by consuming the tissues in narrow channels or gaileries 
extending around its circumference. The presence of these beetles in 
a tree is denoted first by reddish “‘ pitch-tubes”’ or deposits of resin and 
wood dust caused by the beetles’ entrance and later by the yellowing 
of the crown when the tree begins to feel the effect of the girdling. 
The red turpentine beetle (Dendroctonus valens Le Conte) attacks 
the base and roots of the tree. Generally its work is of a secondary 
nature, but occasionally, when very numerous, it 1s the primary cause 
of bath, According to the Bureau of En a ronoines it is also one of 
the primary causes of basal fire wounds.? 
From the Kern River southward a species of flat-head borer ( Melan- 
ophila gentilis Le Conte) causes a considerable loss. The five-spined 
engraver beetle (Ips confusus Le Conte) is occasionally responsible 
for the killing outright of young sugar pines in the sapling or pole 
stage of growth and for the dead tops of many more mature trees. 
Other less important insects do minor damage to various parts of the 
tree. Among these are a weevil (Pissodes yosemite, Hopk.), which 
injures the bark and young saplings; a saw-fly (Lophyrus sp.), which 
damages the foliage, and the sugar pine cone beetle (Conophthorus 
lambertiange Hopk.), which attacks the stems of the young cones as 
well as the cones themselves and causes the latter to fall before 
maturity, thus preventing the maturing of the seed. 
1 Tnquiries i in regard to insects affecting forest trees should be addressed to the Branch of Forest Insects, 
Bureau of Entomology, U. S. Department of Agriculture. 
2 See pages 153-165 of Bureau of Entomology Bulletin 83, Part I, “Practical information on the scolytid 
tiles of North American forests. Barkbeetles of the genus Dendroctonus,’ ” by A. D. Hopkins. 
