44 



oil and nine tenths coal-tar was so sticky after 72 hours that 

 chinch bugs could not cross it, and even at the end of 96 hours- 

 still served its purpose. Mixtures of one fifth oil with coal-tar, 

 and of equal parts of each, were found much less satisfactory.. 

 Diluted with one tenth oil, tar is too fluid to use upon the ground,, 

 as it speedily soaks in; and consequently if this mixture be used, 

 boards must be placed around the field either set on edge or, pref- 

 erably, laid flat, a little strip of ground having been first prepared 

 so that they may be sufficiently bedded in the earth to keep the 

 bugs from passing beneath them. 



As a more convenient and effective means of maintaining a coal- 

 tar barrier, I suggest that strips of sheet" iron bent at the top to 

 form a gutter about one inch across and half an inch in depth at 

 the middle, be placed end to end, slightly overlapping, the tar to- 

 be poured in this gutter. If necessary to prevent too free an 

 escape at the joints, it may be slightly thickened by stirring in 

 dust. Small pits sunk at intervals along a barrier of this descrip- 

 tion would gather the chinch bugs in great numbers, where they 

 could be readily killed with a little kerosene and water, or by 

 mechanical methods. 



STARVATION EXPERIMENTS. 



To ascertain how long the chinch bug in its different stages 

 may live without feeding (a point applying to several field methods 

 of contest with this insect) we confined, September 4, under a 

 bell jar, without food, a miscellaneous lot of bugs of various ages, 

 from the very young of the first stage to adults more than a week 

 old. In twenty -four hours a few of the youngest were dead, and 

 in twenty-eight hours, one adult. In forty-eight hours a number 

 of adults, larvae, and pupae, were dead, and September 7, many 

 more of the last, and almost all the larvae. September 8, only a 

 very few adults and a few pupjB remained; Septembei* 9 five 

 adults were still living, all the others dead; and September 10, 

 six days after beginning, all were dead but one adult. 



This experiment is open to the objection that the bugs were on 

 a table in the office, and the dryness of the air may have had 

 much to do with their death; and as no check lot was separated, 

 it is impossible to say that these specimens were not suffering 

 from one of the diseases prevalent at the time in the region from 

 which they came. 



In an experiment begun August 13, with young bugs, taken as 

 fast as they hatched from the egg and confined without food, none 

 lived twenty-four hours, but most died within twelve. These eggs, 

 began to hatch when fifteen days old. 



A variation in this experiment consisted in burying lots of 

 chinch bugs at the depth practicable by plowing, and examining 

 at intervals to detorinini^ their condition. 



August 13, two lots of larv;e and pupje were buried two inches 

 deep, one with for)d and cme witliout. Forty-eight hours after- 

 ward both \\'('ro niH'overcd and foiiiid niiiiijured, and seventy-two 



