140 



Holt (J. J. H.). The Cockroach : Its Destruction and Dispersal. 

 A Comparison of Insecticides and Methods. — Lancet, London, 

 no. 4840, 3rd June 1916, pp. 1136-1137. 



This paper records the action of various substances on Blatta {Peri- 



planeta) orientalis (common cockroach), tested in the course of some two 



or three years. Prehminary investigations in reference to general 



conditions gave some unexpected results. B. orientalis is able to live 



a long time without food or water, and one individual survived for 



76 days in a petri dish. This insect can also live with a very limited 



air-supply and can survive submersion in water for 20 minutes. It 



eats practically all kinds of organic matter, including its own dead, 



but is soon adversely affected by contact with its own excreta. 



Extensive experiments were made with 25 volatile bodies, 31 aromatic 



oils, 8 coal-tar derivatives, all of which act through the respiratory 



system, 40 dusting pow^ders, most of which act through the respiratory 



system, and 10 food-poisons. With regard to the latter, the tolerance 



of the cockroach for arsenic is remarkable, a lethal result requiring 



41-96 hours. The results of these tests seem to indicate that many of 



the substances which have been supposed to kill cockroaches have 



really had the effect of only driving them away. For rapid destruction 



fumigation with bromine or sulphur dioxide is apparently the best 



method. For domestic purposes, the daily use of creosote, wood 



naphtha, or oil of rosemary, eucalyptus or citronella placed near the 



haunts of cockroaches for two or three weeks should effectually disperse 



them. Where these are inadmissible on account of their smell, 



odourless dusting powders may be used. Of these sodium fluoride 



was found to be the most effective. It is also cheap and keeps 



indefinitely. It is suggested that these experiments may have some 



value as apphed to other insect pests. 



HowARTH (E.). The Destruction of Cockroaches. — Lancet, London, 

 no. 4841, 10th June 1916, p. 1192. 



With reference to the above article, it is pointed out that there is a 

 wide difference between the application of inhalants and food-poisons. 

 No reliable time effect is given by the fact that the lethal effects of all 

 the volatile bodies mentioned are more rapid than the food-poisons, as 

 the former were placed in covered dishes or bottles with imprisoned 

 insects. The only comparable time test would be to use the remedy 

 on cockroaches in their natural habitat. Having to destroy a plague of 

 cockroaches at a large institution in Sheffield, the author fomid fumiga- 

 tion to be, out of the question and decided to poison them in their 

 retreats, so as to avoid their becoming mixed in the food. Their hiding 

 places were easily discovered and the food-poison (Blattis) was laid 

 down there and within three days the pests were dead. The value of this 

 poison lies, in its attractiveness, which is demonstrated by the rapidity 

 with which the cockroaches devour it. Quite different material, a 

 powdery food mixed with a non-volatile poison, had to be used for 

 Lepisma saccharina (silver fish), which in one case was entirely 

 Idlled off in 48 hours. To fumigate dwelhngs and institutions is 

 practically impossible, and an exterminator that produces death in a 

 few hours, with a cumulative effect due to the action of the poison in 

 the bodies of cannibahstic cockroaches, is far more effective. 



