382 SANITARY ENTOMOLOGY 



Pyrethrum Powder 



Dusting with pyrethrum powder is often recommended against roaches 

 but experiments show that for the best results it should be used full 

 strength. It is not to be compared with sodium fluoride in its effectiveness. 



Phosphorus 



A standard remedy for roaches, and one long in use, is phosphorus. 

 This substance is used in the form of a paste composed of sweetened flour 

 containing 1 or 2 per cent of phosphorus. This paste is spread on bits 

 of cardboard and set about where it is easily accessible to the roaches. 



Sulphur 



Sulphur, in the powdered form, scattered about where roaches abound 

 is said to be an eff^ective repellent. 



Castor Oil 



One would scarcely expect this oil to be repellent to the omnivorous 

 roach, but articles smeared with it are said to be rarely attacked by them. 



Of all the poisons and repellents mentioned above, sodium fluoride 

 ranks the highest as an effective roach remedy. 



Traps 



Various sorts of traps have been recommended for catching roaches, 

 but at the best such means only serve to lessen the numbers of roaches, 

 probably never resulting in extermination. 



ENEMIES 



Certain hymenopterous parasites destroy the eggs of cockroaches and 

 there are a number of predaceous insects and other enemies noted as feed- 

 ing on the roaches themselves. The house centipede is recorded as killing 

 the Croton bug and it is said that a toad or a tree frog will clear a room 

 of roaches in one night. 



