224 MONTANA EXPERIMENT STATION. 



THE FLAT=HEADED APPLE=TREE BORER. 



Chrysobothris femorata Fab. 



One of the most troublesome insect pests with which the Mon- 

 tana fruit-grower has to contend, is an apple-tree borer, which in the 

 larval stage is expanded and flattened near the anterior end, as shown 

 in figure 9, a, an appearance which has led to its being called "the 

 ffat-headed borer." Besides attacking the apple, the borer has been 

 recorded also on various other deciduous trees, among which are 

 pear, peach, oak, maple, mountain ash, box-elder, hickory, chestnut, 

 sycamore, horse chestnut, redbud and currant. Mr. F. H. Chittenden 

 of the U. S. Dept. of Agriculture, from whose circular, (Circ. 32, 

 Division of Entomology) many of the facts in this paper are taken, 

 states that cherry, beach and white birch are probably food plants, 

 while an unknown authority has stated that elm, tulip, and cotton- 

 wood are also host-plants. 



Although not considered to be a pest of first class importance 

 this species has been doing a great deal of damage in this state, par- 

 ticularly in the Bitter Root valley, and there is an increasing demand 

 for information concerning its habits and the means of controlling 

 it. It has been particularly destructive on young orchard trees, gird- 

 ling the trunk near the ground and killing the trees. The accompany- 

 ing photograph (see Plate III, Figure 7) shows the manner in which 

 many trees have been affected and killed in Montana. The only ex- 

 planation the writer has to offer as to the cause for the rather unus- 

 ual numbers of this insect, is that under the climatic conditions in 

 Montana trees seem to be affected to a considerable extent with sun- 

 scald, an affection which leaves the trees in an inviting and favorable 

 condition for this insect. It has long been known that this insect 

 prefers for a breeding place trees that have been previously weakened 

 by some other cause. Observation has shown that trees which 

 have been injured on the side exposed to the winter's sun are often 

 selected by the adult in depositing their eggs. 



Young trees are affected principally on the main stem close to 

 the ground, but on old trees the borers work on any part of the tree 

 except the smaller limbs and branches. 



