12 



A thoroughly effective and simple means of ridding one's premises 

 of roaches has been found, however, and is in fumigating with hydro- 

 cyanic-acid gas. The experience of the past few years has demon- 

 strated that this gas, formerly employed for disinfecting nursery stock 

 and orchard trees (notably citrus) from scale and other insects, is 

 equally effective against household insects, and is particularly appli- 

 cable and satisfactory against all species of house roaches. The gas is 

 extremely poisonous to human beings, but, with the proper precau- 

 tions, may be employed with complete safety. A special circular 

 (No. 46 of this series) has been prepared by Doctor Howard, giving the 

 steps of the process in detail. 



The means formerly employed against cockroaches, detailed below, 

 are of value, however, and will be in order where fumigation may be 

 deemed undesirable or is impracticable. 



Poisons and rejyellents. — As just noted, roaches often seem to display 

 a knowledge of the presence of poisons in food, and, notwithstanding 

 their practically omnivorous habits, a very little arsenic in baits seems 

 to be readily detected by them. In attempting to eradicate roaches 

 from the Department storerooms where cloth-bound books are kept 

 various paste mixtures containing arsenic were tried, but the roaches 

 invariably refused to feed on them in the least. This applies particu- 

 Larly 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 consid- 

 erable relief will be gained. It is not a perfect remedy, however, and 

 is at best but a temporary expedient, while it has the additional disad- 

 vantage of soiling the shelves or other objects over which it is dusted. 

 When used it should be fresh and liberally applied. Roaches are often 

 paralyzed by it when not killed outright, and the morning after an 

 application the infested premises should be gone over and all dead or 

 partially paralyzed roaches swept up and burned. Flowers of sulphur 

 dusted about where roaches abound has proved, on the authority of 

 Mr. A. I. Mudd, of this Department, very effective as a repellent. 



There are many proprietary substances which claim to be fairly 

 effective roach poisons. The usefulness of most of these is, however, 

 very problematical, and disappointment will ordinarily follow their 

 application. The only one of these that has given very satisfactory 

 results is a phosphorous paste, sold in the form of pills. It consists of 

 sweetened flour paste containing 1 to 2 per cent of phosphorus, and is 

 spread on bits of paper or cardboard and placed in the runways of the 

 roaches. It has been used very successfully in the Department to free 

 desks from Croton bugs, numbers of the dead insects being found in 

 the drawers every day during the time the poison was kept about. It 

 is also a repellent. 



[Cir. 51] 



