72 
PAPEKS ON INSECTS AFFECTING VEGETABLES. 
have been in their present location for several years and it is impos- 
sible to determine their origin or whether they were infested when 
planted in the garden mentioned. 
GENERAL APPEARANCE AND HABITS. 
The horse-radish webworm (fig. 25) is a beautiful, slender moth 
belonging to the lepidopterous family Yponomeutidse. The wings are 
cream colored with a brownish tinge and have an expanse of about five- 
eighths of an inch. The moths are shy and hide among the foliage of 
infested horse-radish plants. When disturbed they fly readily for a short 
distance and usuallypromptlyhide. In captivity they feed eagerly on 
diluted honey. 
The eggs (fig. 26, c) 
are scale like and are 
usually deposited 
singly on the upper or 
lower sides of the 
leaves. - 
Fig. 25.— ThehJrse-radish webworm (Plutella arrnoracia): Moth, 
side view, ak>ve; moth with wings spread below. Enlarged. 
(Original.) 
-e. 
Fig. 26. — The horse-radish web- 
worm: a, Larva, lateral view; 
b, larva, dorsal view; c, egg. 
All enlarged. (Original.) 
The newly hatched larva? are pale yellow. The mature larvae 
(fig. 26, a, b) are yellowish green, with a more or less distinct yellow 
or or/tnge band across the dorsal surface near the middle. Almost 
immediately after hatching the larvae spin compact webs under 
which they rest and feed until mature. The webs are white or gray 
acd are remarkably close-meshed. When the horse-radish plants 
are young the larvae web together and feed on the first spikelike 
leaves and later a favorite location is among the blossom buds. With 
older plants the larvae feed on the leaves generally, usually selecting 
the most tender ones. 
