188 Annual Report for 1905 of the Zoologist. 
caterpillars which hatch out in a few days generally continue 
feeding not only through the summer, but during the autumn 
and winter, except in very severe weather, not turning into 
chrysalids till the following spring. Just before they turn 
(usually late in April) they are particularly voracious, and do 
much harm. 
It has often been suggested that advantage might be taken 
of the habit these moths have of hying to a light, and many 
“ trap-lanterns " have been devised as remedies for these and 
other pests. There may be cases in which trap-lanterns would 
be useful against an insect pest, but three conditions would be 
necessary : it would have to be strongly attracted by the light ; 
females (and not males only) would have to succumb to the 
attraction ; and, most important of all, the time of flight would 
have to be very definite, and limited 
to a few days. Elaborate experi- 
ments have shown that the general 
use of trap-lanterns throughout the 
summer is far more harmful than 
beneficial. The results obtained 
some years ago by Mr. Slingerland 
at the Cornell University were most 
instructive. Most of the insects 
caught were neutral as regards 
agriculture, and of those which 
had any economic importance, the 
useful insects caught equalled or 
even out-numbered the injurious. 
Of the Noctua moths captured 88 
per cent, were males, though both 
sexes are winged, and the females 
which came to the lamps had mostly 
laid their eggs. On the other hand 
a nearly equal percentage of the 
useful ichneumon flies taken were females, just the individuals 
most important to preserve. 
We seem reduced, therefore, to waging war upon surface 
caterpillars in the grub stage, and this is a troublesome 
business. On the farm it is important to keep down charlock 
and other cruciferous weeds ; to disturb the ground by frequent 
harrowing during an attack, so as to turn the grubs up for 
the birds ; to encourage the crop by forcing manures ; and 
especially to try and clean the ground when next free of crop 
by a dressing of lime or gas-lime ploughed in. 
In market gardens it would certainly pay to do more than 
generally is done in the way of hand-picking, particularly 
at night with lanterns, for it is chiefly at night that the 
FIG. 2. — Injury by surface 
caterpillars. 
