43 
might possibly be used, however, with a proper apparatus, against 
the hard and partly dead stalks and lower leaves, to kill such 
chinch bugs as were not in any way protected from its momen¬ 
tary contact. 
Our experiments were as follows: Varying numbers of chinch 
bugs, adult and young, were rapidly deadened September 13, 1888, 
by a very few seconds’ exposure to steam thrown against them 
through a half-inch rubber tube as they rested on a sheet of 
paper. A few hours later most of them showed signs of reviving 
life, but the next day all were dead. 
Other insects exposed to the steam jet were as readily killed: 
maple plant lice in one or two seconds—the leaves bearing them 
remaining uninjured; grasshoppers and blister beetles (Epicauta) in 
six or seven seconds. 
Steam was passed rapidly over a young foliage plant (Coleus) 
for seven seconds without noticeable injury; but growing oats 
showed slight injury after three seconds’ steaming and with 
longer exposure was much damaged. 
Application of steam to shrubs and trees seemed to be imprac¬ 
ticable, because of the difficulty of equal distribution. If used in 
large quantities the steam would kill the leaves nearest the jet 
before insects on others wrnre affected, and if in smaller quantities 
the time and care required to throw it uniformly against all sur¬ 
faces and from various directions would make it much less effec¬ 
tive and convenient than a fluid spray. 
BARRIERS TO MIGRATION. 
Coal-tar .—The use of coal-tar as a barrier to the passage of the 
bugs from field to field at harvest time, is a well-known and highly 
valuable measure, one of the most important in the list of defences 
against this insect, but has the practical disadvantage that the 
belt of tar poured along the ground or painted on boards speedily 
dries out, and must be renewed in hot weather two or three times 
a day, or even oftener, to completely prevent the passage of the 
bugs. 
Chinch bugs surrounded with a line of fresh tar will sometimes 
escape by wading through it, but all such bugs die in an hour or 
so, as we have determined by capturing and confining them under 
observation. 
Coal-tar and oil .—To retard the drying of the tar, it may be 
mixed with oil or other grease, machine oil being perhaps the 
cheapest for common use. Soap grease, tried out, would doubtless 
answer the same purpose. 
The advantage of this mixture is shown by some experiments 
made at the office in August and September, 1888, when tar, 
unmixed, poured on paper and placed in the hot sunshine, 
dried in half an hour so that bugs could cross it here and there 
without daubing their feet; while a mixture of one tenth linseed 
