AMERICAN PLUM BOEEE. 5 



FOOD PLANTS. 



This insect does not, by any means, confine its attacks to plum. 

 It has been taken feeding upon plum, peach, cherry, Chinese plum 

 (Prunus simoni), Kieffer pear, mountain ash, persimmon, apple, 

 and Russian mulberry. The writer has found it equally abundant 

 on plum, cherry, peach, and apple. It will probably attack the 

 trees of any of the common stone or pome fruits when the proper 

 conditions are presented. 



FEEDING HABITS AND CHARACTER OF INJURY. 



As has already been stated, the food habits of this insect are of 

 especial interest when contrasted with those of other wood-boring 

 species. The plum borer prefers trees which are not dead and yet 

 are not in a too vigorous condition. The attention of the writer was 

 first attracted to the work of this borer by an apple tree upon which 

 it had established itself. This tree had been partially girdled by a 

 disease commonly known as collar blight. Under the skirt of bark 

 bordering the wounded area the borer had begun its work and by 

 extending its galleries out into the living tissue had completed the 

 girdling of the tree. This seems to be the characteristic form of 

 injury for the species. Beginning at some scar, wound, or crevice, 

 where a bark scale offers partial protection, the larva works its way 

 back into the living tissue, in broad, shallow, irregular galleries just 

 beneath the bark. Apple trees partially girdled by collar blight and 

 trees injured mechanically by frost or by some other factor offer the 

 ideal condition for the work of this borer. Without injury of some 

 sort to its host plant the borer rarely succeeds in establishing itself, 

 and entirely healthy and uninjured trees are in little danger from its 

 attacks. On the other hand, where a tree has suffered injury the 

 work of this borer may, in many cases, considerably shorten its fife. 

 PI. I, a, h, c, shows the character of the galleries and the condition 

 of trees most liable to attack. 



DESCRIPTION OF STAGES. 



THE EGG. 



When first deposited the egg appears as a regular oval, opaque 

 white body, eoarsely punctate. The size is fairly uniform, the average 

 for 10 being 0.59 mm. by 0.42 mm. A marked change takes place in 

 the appearance of the egg as incubation proceeds. Twenty-four 

 hours after deposition the color changes from white to a pinkish lint, 

 or in cases where incubation is somewhat delayed to a Hghl brown, 



i in is hours to ;i dull red. In three to four days a slight depres- 

 sion appears in the center and 2\ hours before batching the eolor 



