66 Farmers’ Bulletin 1169.° 
lay their eggs in them. The grubs hatching from these penetrate 
the bark and spend the winter direetly under it. The following 
spring they resume feeding and keep it up until full grown, where- 
upon they bore into the wood, through it to the pith, and make a 
3 to 4 inch gallery along that, filling it with wood fiber and pupating 
at one end of it. Thus the life cycle, although completed within a 
twelvemonth, extends from one calendar year into the next. 
Remedies.—Cut out and burn all infested wood before May or June, 
thus preventing the grubs from reaching maturity and propagating. 
It appears possible also to control the insect by thoroughly coating 
the bark in July withlead arsenate (p. 11) or by painting trees with 
kerosene emulsion (p. 12, 13) in April or thereabouts. 
Fic. 46.—The cottonwood borer: Larva, side view. Enlarged. (Milliken.) 
COTTONWOOD BORER.” 
Destructiveness.—Iin the Middle West the cottonwood borer is very 
destructive to poplar or cottonwood and willow trees in all stages of 
erowth. The mines of the borer, made at the base of the stem, often 
girdle the tree, causing its death or so reducing the strength of the 
wood that it is broken off by the wind. 
Evidence of infestation.—Broken-off trees, sickly tops, and collec- 
tions of shredded boring dust on the surface of the ground beneath 
the trees indicate the presence of the borers. On removal of the bark 
at the surface of the ground borer mines are disclosed. 
Description and habits—The cottonwood borer is a yellowish, 
elongate, cylindrical grub (fig. 46). It hatches from an egg laid 
by a large, black and white mottled, longhorned beetle (fig. 47). 
The eggs are laid during July and August in small punctures made 
in the bark at or just below the surface of the ground, and the borers 
8? Plectrodera scalator Fab. 
