798 
In the fall, when the beetles have ma- 
tured, if some of the burrows are opened, 
both males and females can be found, 
the females usually outnumbering the 
males four or five to one. 
During the hibernation period the 
adults apparently do not feed, as the 
fungus upon which the larvae feed is al- 
most entirely absent in burrows opened at 
various times during the winter and 
there is no evidence of wood burrowing. 
Fig. 83 The Shot Hole Borer (Xyleborus dis- 
ar). A, Larva; B, Pupa; C, Adult Female; 
, Adult Male; H, Hegs. 
Host Plants 
This insect will apparently work and 
develop in all kinds of deciduous fruit 
and forest trees and has been reported 
as working in conifers. The following 
fruit trees are reported: apple, pear, 
quince, cherry, prune, plum, hawthorn, 
apricot, white hawthorn, grape and pome- 
granate. Nearly all writers on this sub- 
ject agree that the beetles favor dying 
trees to healthy ones and several of them 
state that freshly cut logs and stumps are 
excellent breeding places. In the North- 
west we have found them working in 
cherry, prune, apple, pear and chestnut. 
Cherry and prune are attacked more be- 
cause those two trees appear to be more 
subject to diseased conditions than any 
of the others. Many cherry trees, espec- 
ially young ones, die each year from the 
disease known as cherry gummosis. 
Prune trees are found growing in all man- 
ner of places and a great many in unsuit- 
able surroundings. Naturally many of 
them succumb, and in addition there 
seems to be a disease similar to that of 
the cherry which destroys a great many. 
Both of these fruits develop what is com- 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
monly known as sour sap, a condition 
known to be favorable for the develop- 
ment of the fungus food upon which the 
larvae feed. 
An occasional apple orchard is found 
infested, and I have observed a few pear 
trees showing attacks of this insect. 
The Food of Xyleborus Dispar 
The fungus upon which the larvae 
feed is evidently carried to the burrows 
by the females, since it appears in each 
burrow almost as soon as started. 
The earlier entomologists seem to have 
been in doubt as to the nature of the 
food found in the brood chambers. Hub- 
bard, 1897, gives a discussion on this 
fungus. He writes as follows: 
“The ambrosia does not make its ap- 
pearance by accident or at random in the 
galleries of the beetles. Its origin is en- 
tirely under the control of the insect. It 
is started by the mother beetle upon a 
carefully packed bed or layer of chips, 
sometimes near the entrance, in the bark, 
but generally at the end of a branch gal- 
lery in the wood. In some species the 
ambrosia is grown only in certain brood 
chambers of peculiar construction. In 
others it is propagated in beds, near the 
cradles of the larvae. The excrement of 
the larvae is used in some and probably 
in all the species to form new beds or 
layers for the propagation of the fungus. 
“There must be present a_ certain 
amount of moisture or sap, and the sap 
in most species must be in a condition of 
fermentation.” 
As the fungus develops the growth 
forms into little globules containing the 
spores. 
“The young larvae nip off these tender 
tips as calves crop the heads of clover, 
but the older larvae and the adult beetles 
eat the whole structure down to the base, 
from which it soon springs up afresh, ap- 
pearing in little white tessellations upon 
the walls.” 
Natural Enemies 
EKichhoff, 1881, reports Calydium fili- 
forme, Oxylaunus caésus and Hypophlosus 
bicolor as found in the chambers of Xyle- 
borus dispar and probably feeding upon 
the brood and eggs of the latter. 
