APPENDIX. 353 



opinion has been expressed that injury known under this name is in reality 

 due to the work of this species of borer. The beetle is essentially a sun- 

 loving species and deposits its eggs practically exclusively on the southern 

 or southwestern sides of standing trees or on recently felled logs that are 

 exposed to direct sunlight. Observation shows that it is doubtful if the 

 young larva? would be able to withstand the strong flowing sap of vigorous 

 trees. 



Infestation may be detected by the discoloration of the bark. 



A list of its recorded food plants includes, among orchard trees, apple, 

 pear, peach ; and of shade and forest trees, mountain ash, oak, maple, box- 

 elder, hickoi'y, chestnut, sycamore, horse-chestnut, linden and willow. To 

 this list should be added plum and cultivated redbud ( Cercis japonica), fx"om 

 which the species has been reared by the writer, and currant.* 



Cherry, beech, and white birch are probably food plants, although the 

 beetle has not been reared from them, and elm, tulip, and cottonwood have 

 been mentioned as such, but on what authority is not clear. Oak is without 

 doubt the natural host tree. 



The larva differs greatly from that of the round-headed borer. Its name 

 of flat-headed borer is derived from the peculiar flat expansion of the second 

 thoracic segment, the one just behind the head. In color it is a light yellow, 

 and in length it measures nearly twice that of the mature insect. It habit- 

 ually rests in a curved position, more bent usually than shown in the illus- 

 ti^ation ( Fig. 3, a ). The pupa ( b ) shows the form of the future beetle and is 

 of the same yellow color as the larva. 



This species inhabits practically the entire United States and the southern 

 portion of Canada, being like the preceding, a native of North America and 

 injurious year after year. 



NATURAL HISTORY AND HABITS. 



The beetles make their appearance about the same time as the round- 

 headed borer, in regions infested by both species, in the principal apple- 

 growing regions of the northern states after the middle of May, and con- 

 tinue through the month of July, and, it is said, even into September, the 

 female depositing her eggs upon the trunks or branches of trees destined to 

 be the future food of the larva, in cracks and grooves or under bark scales. 

 Several eggs are most frequently found together. The eggs are yellow in 

 color, irregularly ribbed, and about one-fiftieth of an inch in length. f The 

 larva differs from the round-headed borer in that it requires only a single 

 year for its development, pupation occurring in the spring shortly after the 

 appearance of the beetles. It diffei'S also in its manner of work, living for 

 the most part just beneath the bark, where it excavates broad, flat, and very 

 irregular channels, but sometimes entering more deeply into the sap-wood. 

 Like many other borers it often girdles a small tree, a single individual 

 being capable of killing a small tree in this manner. As it approaches 

 maturity it generally eats deeper into the solid heart-wood, but in 



*P. H. Hillman, Nevada Experiment Station, Bull. 36, p. 18. 

 tC. V. Riley, Proc. Fnt. Soc. Wash., Vol. Ill, p. 92. 

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