UNITED STATES DEPARTMENT OF AGRICULTURE 
Wfe BULLETIN No. 424 A 
li^S-^il^-? Contribution from the Bureau of Entomology < 
itomology 
^C^-^t L. O. HOWARD, Chief jO^"^L 
Washington, D. C. PROFESSIONAL PAPER November 9, 1916 
THE COTTONWOOD BORER. 1 
By F. B. Milliken, Scientific Assistant, Truck-Crop and Stored-Product Insect 
Investigations. 
INTRODUCTION. 
When the writer was stationed at Garden City, Kans., in 1913, 
some of the first inquiries he received were for methods of preventing 
injury by borers to shade trees — cottonwood (Populus deltoides) and 
willow (Salix alba). Neither entomological literature nor inquiries 
made of other entomologists regarding the cottonwood borer yielded 
accurate information upon which remedial measures might be based. 
Investigations were begun, therefore, to determine the life history 
and habits of the insect. Its large size and the obvious character of 
the injury it accomplishes have facilitated the securing of results, 
which are here given. 
DESCRIPTION. 
THE ADULT. 
The cottonwood borer (Plectrodera scalator Fab.) is one of the 
largest beetles found in Kansas, the male measuring from 1.25 (3.2 
centimeters) to 1.375 inches in length by 0.40 inch (1.1 centimeters) 
in greatest width, and the female about 1.5 inches long (3.5 centi- 
meters) by 0.50 inch (1.2 centimeters) in width. The ground color 
in both sexes is shining black overlaid by stripes and patches of 
cream-colored scales. On each elytron the black shows through in 
two rows of irregularly rectangular patches, and there is a black 
patch on each side and one on the top of the prothorax. The an- 
tennae are black, except the first two segments, which, with the legs, 
appear rusty or grayish from a scattering covering of the light 
scales. Much of the ventral surface is also covered with light scales, 
although not so thickly as the dorsal. In both sexes the prothorax 
1 The investigations of the cottonwood borer (Plectrodera scalator) were begun prior to 
the reassignment of shade-tree insect problems to the Branch of Forest Insect Investiga- 
tion. — F. H. Chittenden. 
55508° — Bull. 424 — 16 
