EXPERIMENTS AGAINST COCKROACHES. 



13 



a given cage, shows that they act too slowly to commend themselves 

 for general use. Barium carbonate and mercuric chlorid are the 

 only materials that would appear to warrant further tests, and there 

 is no indication that they will approach the effectiveness of sodium 

 fluoric! . 



As only one of these mixtures (test No. 3) contained any sub- 

 stance that might serve as a bait, it is evident that their efficiency 

 must be due to their being taken into the mouth by the roach when 

 the appendages are cleaned. This conclusion is. strengthened by the 

 results of dipping tests, where roaches clipped in arsenic trioxicl or 

 sodium arsenite died in less than 48 hours. 



It should be emphasized that arsenious oxid and mercury bichlorid 

 are far too poisonous to human beings to be generally used as roach 

 remedies wider average dwelling conditions. 



Hellebore, while poisonous to insects when taken internally, acts 

 so very slowly that it can not be classed as a roach remedy. 



In the test of paradichlorobenzene 8-J pounds of this material were 

 exposed for 44 hours at a temperature of about 80° F. in a room the 

 capacity of which was 846.5 cubic feet. The roaches were placed on 

 the floor in two cages, and even this heavy fumigation, with the in- 

 sects fully exposed, failed to kill 50 per cent. 



MISCELLANEOUS POWDERS INEFFECTIVE. 



The following list of various powdered materials tested, unadulter- 

 ated, was found to be ineffective against roaches. Not less than 40 

 roaches were used in the cage tests, and the experiments were con- 

 tinued for at least a week. The room tests were made in badly in- 

 fested rooms or kitchens and were generally continued for seven 

 days. The method of testing is indicated in parentheses after the 

 name of the material. 



Miscellaneous powders ineffective against cockroaches. 



Allspice (cage). 



Angelica root (cage). 



Anise seed (cage). 



Barium sulphate (cage). 



Calcium carbonate (cage and room), 



Calcium hydroxid (room). 



Calcium oxid (cage and room). 



Calcium sulphate (cage and room). 



Camphor (cage and room). 



Cassia (cage). 



Chamomile flowers (cage). 



Charcoal (room). 



Cloves (cage). 



Colocynth pulp (cage and room). 

 Cornstarch (room). 

 Corn meal (room). 

 Dolomitic lime (cage). 

 Eucalyptus leaves (cage). 

 Ferric oxid (room). 

 Ferrous oxid (room). 

 Flint, ground (cage). 

 Fuller's earth (room). 

 Gypsum (cage and room). 

 Lead carbonate (cage and room). 

 Lime, air-slaked (cage and room), 

 Magnesium carbonate (room). 



