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' exp'osure 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 were 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 fest; while a mixture of one tenth linseed 



