2 BULLETIN 966, U. S. DEPARTMENT OF AGRICULTURE. 
Two other webworms affect horse-radish in the United States, both 
introduced from abroad, namely, the imported cabbage webworm 
(7)* and the diamond-back moth (Z0).° 
DESCRIPTION. 
THE MOTH. 
The moth of this species is rather bright ocher yellow and the 
forewings are traversed by two irregular lines dividing the wing into 
thirds of nearly equal 
width. Near the tip of the 
forewing is a conspicuous 
hghter spot and another 
larger rounded one near 
the middle of the anterior 
border. Directly outward 
from this latter there is an 
angular 8-shaped spot. 
The wing expanse is about 
1 inch (25 mm.) and the 
iength of the body a little 
less than half an inch (10 
mm.). This moth resem- 
bles in general contour the 
related /’. rimosalis Guen., 
but may be readily distin- 
euished by the characters 
given and with the aid of 
the accompanying illustra- 
tion (fig. 1). In some in- 
dividuals the outer edge of 
the forewing is much 
Fig. 1.—Huropean horse-radish webworm (Hvergestis (darker than in others, 
straminalis) : a, Moth, normal form; 6, moth, ; 
dark form. Twice natural size. darker even than in i 
rimosalis. 
The following more technical description is after Meyrick (4, p. 
42h): 
Fore-wings pale ocherous-yellow, sprinkled with dark brown, veins pos- 
teriorly dark brown; lines dark fuscous, first angulated above middle, angu- 
larly indented above angle, second unevenly curved; an angularly 8-shaped 
discal spot, outlined with dark fuscous, touching angle of first line; a cloudy 
dark fuscous subterminal line, forming above middle a strong dark suffusion 
inclosing a pale terminal spot. Hindwings prismatic yellow-whitish; traces 
of a dark posterior line; termen narrowly dark fuscous. 
5 Hellula undalis Fab. 
® Plutella maculipennis Curt. 
a ee 
