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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
and are small, stout, cylindrical, brownish black beetles, about three 
millimeters, or an eighth of an inch long. The habits of the two 
species are very similar, so they are discussed together. Both are 
native to California. Dr. Hopkins, in an article in 1903, mentioned 
the fact that the former was a twig pruner. The writer has discovered 
that P. cristatus is also responsible for part of the injury. 
Both breed in a number of cypresses and cypress-like trees, and may 
even be found working together in the same tree. They attack in 
numbers and excavate galleries several inches long under the bark, 
parallel to the grain of the wood, and lay their eggs in small niches on 
each side of the galleries. Upon hatching, the larvae mine away from 
the galleries in the cambium and thus girdle the trees, transforming to 
beetles at the ends of the mines, P. cupressi pupating under the bark 
and P. cristatus a short distance in the wood. 
Under certain conditions, part of the emerging young beetles attack 
small branches about one-eighth inch in diameter, entering through 
the bark and mining down the centers of the twigs, leaving nothing 
but thin exoskeletons of bark to support the tips. Consequently, 
many twigs break down from their own weight. The beetles may do 
this in order to obtain food or to await the coming of their team¬ 
mates in order to make a concentrated attack on the next tree. Beetles 
are very seldom found dead in a twig burrow, which fact helps to sub¬ 
stantiate the theory that the beetles leave them to make brood gal¬ 
leries and rear young elsewhere. One female removed from a food 
burrow and placed in a cage with a section of cypress, proceeded to 
make a short gallery under the bark and lay eggs therein. They were 
apparently infertile, for none hatched, on account of the male placed 
in the cage having failed to find the gallery of its mate. 
Both sexes have been found in the twigs, but always only one beetle 
to a gallery. They have been captured in the following months: 
March, June, July, August, October, November and December. 
Upon careful search, however, they probably could be found during 
the other months as well. Most of this work is done in the spring and 
fall, while a majority of the injured twigs drop from the trees during the 
first heavy windstorms of the fall. Part of the injuries to the trees 
heal over after being abandoned, but usually a distinct swelling or 
elbow remains at the point of attack. 
To indicate the number of twigs which are often pruned from a single 
tree, the writer raked together those under an ordinary sized monterey 
cypress and thus obtained a pile two and one-half feet high and nearly 
as wide, and still many more remained on the tree, giving it a very 
dilapidated appearance. 
Phloeosinus twig work has been noted on the following cypresses:— 
