15 
INSECT ENEMIES OF THE FOLIAGE. 
Little time was had to collect or study the enemies of the foliage, 
but from general observations there was no perceptible injury from 
this class of depredators. 
NATURAL ENEMIES OF THE DESTRUCTIVE AND INJURIOUS 
INSECTS. 
Numerous species of predaceous and parasitic insects were found 
associated with the primary and secondary enemies. Some evidence 
was found of the beneficial work of birds, and a few examples of the 
pine-destroying beetle were found that had been killed by a disease, 
but in no case was there sufficient evidence to indicate that any of 
these natural enemies, or all combined, were in sufficient numbers to 
render any special service toward bringing the trouble to an end. 
They were undoubtedly rendering some service, however, in prevent- 
ing the rapid multiplication of the pine destrover, which would other- 
wise occur. 
PREDACEOUS ENEMIES. 
The bluish-green predaceous beetle ( Trogosita virescens Fab.).—This is 
an elongate, flattened, shining, green beetle, varying in length from 
10 mm. to 13 mm., and in width from 3 mm. to 4 mm. The larva 
is a long, slender, reddish to whitish worm, with shining black head 
and prothoracic pilates. This recognized predatory enemy of bark- 
infesting insects was frequently found associated with colonies of the 
pine-destroying beetle and the secondary enemies, and a few adults 
were found hiding beneath the flakes of outer bark. This widely dis- 
tributed insect in North America has not been sufficiently studied to 
determine its true relation to the destructive enemies of the trees, but 
it is evidently quite beneficial. 
Clerid beetles and their larve.—The slender, reddish larve of unde- 
termined species of this class of predaceous enemies of bark beetles 
were found in small numbers in the bark with the broods of the 
destructive and other species of bark beetles. This class of beneficial 
insects usually renders great service in reducing the numbers of the 
destructive and injurious species. Therefore their scarcity in this 
region may have had much to do with the rapid multiplication and 
spread of the pine-destroying Dendroctonus. While collecting speci- 
mens of bark beetles from saw logs in a mill yard at Boulder, Colo., 
on August 25, one of these Clerids (Clerus nigriventris Lec.) was very 
common. The active, ant-like adults, which are black, marked with 
transverse patches of gray, vary in length from 6 mm. to 8 mm., and in 
width from 2.5mm. to3mm. The larva is a slender, pale red worm. 
The adult feeds on and destroys great numbers of the adult bark 
