93 
several times repeated, with the same average results. Even where 
the vines were smoked so strongly as to slightly scorch some of the 
leaves, the lice were not all killed. 
The vapor of bisulphide of carbon was used more as a satisfaction 
to curiosity than for any other reason. Several leaves with plant- 
lice were placed under a bell-jar with a cubic inch of sponge steeped 
with the poison, and left exposed to the fumes for ten minutes. 
When examined, all were dead, and did not revive after an hour’s 
exposure to the air. Five minutes exposure was^ hardly sufficient, 
however, as the bugs, though seemingly dead at first, recovered in 
about three-quarters of an hour, and began to crawl about. 
As a result of these experiments, we may say that no effective 
remedy was found applicable on a large scale, except at an expense 
which would considerably outweigh the benefit, especially as the 
probabilities are that the natural enemies of the plant-lice will put 
a stop to their ravages even sooner than artificial measures can do. 
For garden application I think tobacco smoke the most feasible 
remedy, but it should be applied repeatedly, and care should be taken 
to first shake and stir the vines, to drive away any of the winged 
parasites of the lice, which would otherwise be sacrificed with their 
hosts. There is little probability that the larvae of these parasites 
which are still within the bodies of the lice, would be injured by the 
smoke. Some form of the kerosene mixture would probably answer 
nearly as well, except that it would doubtless kill these larvae, and so 
retard the parasitism of the pests. A simple mixture of about one 
part of kerosene to twenty of water, would probably answer for this 
purpose, if kept agitated, &s well as the emulsion. A remedy strongly 
recommended by Kaltenbach and some other European authors, is a 
weak solution of common salt, (one and one-half to two per cent.), 
thoroughly applied two or three times to the surface of the plant. 
NATURAL ENEMIES 
The natural enemies of these lice are of the usual kinds, and at¬ 
tack this species with their customary vigor. They include the 
common Cpccinellidee and their larvae, the larvae of Syrphus flies, 
and hosts of the parasitic Aphidius, which lays its eggs in the bodies 
of the lice. The extent to which this parasitism prevails at any 
given time, is a good index of the time the pest is likely to last, as 
the parasites, when once well started, multiply very rapidly, and 
will soon reduce the number of their hosts to insignificance. A par- 
asatized louse may be recognized at a glance by the swollen body 
and the pale brown color—very different from that of the living in¬ 
sect. Where any large percentage of these are seen, only some 
unlucky turn of affairs can prevent the speedy suppression of the 
plant-lice, and the owner need waste little further anxiety on them. 
The completeness of their disappearance at Normal may be inferred 
from the statement already made of the difficulty of finding a few 
specimens, about the middle of September, in the worst infested 
field in that vicinity. 
