190 REPORT OF STATE GEOLOGIST. 



other insects, is equally effective against household insects, and is 

 particularly applicable and satisfactory against all species of house 

 roaches. The gas is extremely poisonous to human beings, but by 

 observing the proper precautions, may be employed with complete 

 safety. A special circular (No. 4fi, Second Series, U. S. Div. Ent.) 

 has been prepared by Dr. L. 0. Howard, giving the steps of the pro- 

 cess in detail. 



"In addition to the hydrocyanic-acid gas treatment noted above, 

 two or three other forms of fumigation may be employed against 

 house roaches. ^V^le^ever roaches infest small rooms or apartments 

 which may be sealed up nearly air-tight, and also on shipboard, the 

 roach nuisance can be greatly abated by the proper use of poisonous 

 gases, notably bisulphide of carbon. This substance distributed about 

 a pantry or room in open vessels, will evaporate, and, if used at the 

 rate of one pound to every- 1,000 cubic feet of room space, will de- 

 stroy roaches. Unless the room can be very tightly sealed up, how- 

 ever, the vapor dissipates so rapidly that its effect will be lost before 

 the roaches are killed. The hatches of ships, especially of smaller 

 coasting vessels, may be battened down, a very liberal application of 

 bisulphide of carbon having been previously made throughout the in- 

 terior. If left for twenty-four hours the roaches and all other vermin 

 will unquestionably have been destroyed. In the use of this substance 

 it must be always borne in mind that it is violently explosive in the 

 presence of fire, and every possible precaution should be taken that 

 no fire is in or about the premises during the treatment. It is also 

 deadly to higher animals, and compartments should be thoroughly 

 aired after fumigation. 



"Poisons and EepclJcnis. — As just noted, roaches often seem to 

 display a knowledge of the presence of poisons in food, and, notwith- 

 standing their practically omnivorous habits, a very little arsenic in 

 baits seems to be readily detected by them. In attempting to eradi- 

 cate roadies from tlie Departinont storerooms, wlierc cloth-bound 

 books are kept, various paste mixtures containing arsenic were tried, 

 but the roaches invariably refused to feed on them in the least. Tliis 

 applies particularly to the German roach, or Croton bug, and may not 

 hold so strongly with the less wary and perhaps less intelligent larger 

 roaches. 



"A common remedy suggested for roaches consists in the liberal 

 use of pyrethrum powder or buhach, and when this is persisted in 

 considerable relief will be gained. It is not a perfect remedy, how- 

 ever, and is at best but a temporary expedient, while it has the addi- 

 tional disadvantage of soiling the shelves or other objects over which 



