USE OF GASES AGAINST HOUSEHOLD INSECTS 459 



which it attacks slightly. The gas does not bleach or 

 injure household fabrics. It is also a real deodorant, for it 

 acts chemically upon the gases causing the odor, and forms 

 others without any smell. 



Notwithstanding all the good points in favor of formal- 

 dehyde as a disinfectant it is not an insecticide. Although 

 it will kill those minute plants, bacteria, it will not kill, 

 to any extent, those small animals, insects. There are 

 several experiments on record to show that formaldehyde 

 will kill very few insects even when unusually large quanti- 

 ties of the gas are liberated in an air-tight space. 



" The Public Health and Marine-Hospital Service report 

 formaldehyde as not possessing insecticidal properties 

 against mosquitoes." C. L. Marlatt proved by experi- 

 ment that even though the gas was generated to three or 

 four times the amount necessary for disinfection purposes it 

 only killed a few angoumois grain moths and apparently 

 did not injure bean weevils at all. C. P. Lounsbury, 

 South Africa, reports that the gas did not kill bedbugs 

 although it apparently killed some house-flies and aphids 

 during an exposure of two days. Lampert of Germany 

 found that formaldehyde would not kill insects. M. V. 

 Slingerland found that bedbugs and cockroaches were not 

 killed after a thorough fumigation for twenty-four hours. 



All the evidence the writer can find seems to show con- 

 clusively that formaldehyde has so little value as an insec- 

 ticide that it should never be used for that purpose. 



THE USE OF HEAT AGAINST INSECTS 



Within the last few years heat has been used to some 

 extent in mills in the western part of the United States, at 



