402 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



hens did not "set well," it is impossible to determine the exact cause 

 of this high mortality. 



The failure of these eggs to control lice is probably due to the fact 

 that naphthalene vapor is over four times heavier than air and, there- 

 fore, does not work up through the feathers, although, as previously 

 mentioned, a certain amount is taken into the hen's body, probably 

 from' direct contact with the egg. 



It might be added that in many of the tests the nests and even the 

 naphthalene eggs themselves were found to be swarming with chicken 

 mites {D. gallinw Redi.). 



Summary 



1. Powders containing 5 per cent or less of naphthalene are of no 

 value against lice. 



2. Powders containing from 10 per cent to 20 per cent are very 

 effective. 



3. As little as 10 per cent naphthalene may temporarily injure hens, 

 if the powder is well rubbed in, and 60 per cent or more may kill the 

 treated fowls under the same conditions. 



4. Naphthalene (60 to 100 per cent) sprinkled over the backs of 

 fowls at roost proved to be of considerable value against lice. 



5. Naphthalene nest eggs are of no value against lice on laying or 

 setting hens. 



6. The data obtained indicate that setting hens, the eggs and possi- 

 bly any chickens hatched are injured by these eggs. 



THE DEPLUMING MITE OF CHICKENS: ITS COMPLETE 

 ERADICATION FROM A FLOCK BY ONE TREATMENT 



By H. P. Wood, U. S. Bureau of Entomology 



During the course of experiments with the control of poultry lice 

 a few flocks infested with the depluming mite^ were encountered.^ 

 Inasmuch as treatments heretofore have consisted merely of ointments 

 applied to the parts visibly affected, it was deemed worth while to 

 attempt to find a method of completely destroying the mites in an 

 infested flock. After a few preliminary experiments we were fortunate 

 in discovering a method which has obtained the desired results. 



The depluming mite is found in a scale surrounding the base of the 

 feathers. To discover the mite on infested fowls it is only necessary 



1 Known scientifically as Cnemidocoptes gallince Railliet. 



2 This investigation was carried out at the Dallas, Texas, laboratory of the Bureau 

 of Entomology, under the direction of Mr. F. C. Bishop. 



