EXTEBNAL PARASITES 239 



too much. Just a small amount is sufBcient to close the 

 breathing pores of the lice and kill them by asphyxiation. 



Treatment. — The older birds are best treated by either im- 

 mersing in a good coal-tar solution, as a 1 per cent, kreso dip, 

 or by dusting with an insecticide. 



A very effective insect powder is made by taking crude car- 

 bolic acid, 1 pint, and gasoline, 3 pints, mixing with sufficient 

 plaster of Paris to make a slightly moist mixture, then run 

 through a sieve made of a piece of common fly-screening. 

 It will take about 2)4, pounds of the plaster of Paris. Allow 

 the screened mixture to lay on the table on the paper where it 

 was sieved for about two hours, when the powder will be found 

 to be dry. It is now ready for use. If it is not used at once 

 it must be kept in a container with a tight-fitting lid, as an 

 old baking-powder can. It soon loses its good properties if 

 exposed to the atmosphere. Take an old talcum can or a 

 small baking-powder can and punch the top full of holes by 

 aid of a nail and hammer, and use as a sifter as you use a pep- 

 per-box. (See Fig. 97 for illustration of method of holding 

 bird and dusting.) 



In applying the powder to the bird, with the left hand grasp 

 the bird, holding it head down, dust a small quantity of the 

 powder down into the feathers, rubbing the feathers the wrong 

 way, working the powder down to the skin. 



Dust all parts of the body. A bud thoroughly dusted need 

 not be redusted for three months unless the houses are badly 

 infested, under which conditions a systematic cleaning, scrub- 

 bing, and spraying with a strong coal-tar disinfectant, as a 2 

 per cent, creolin solution, must be carried out. 



Dust all hens at time of setting, and again the day they are 

 taken from the nests. 



CHIGGER 



Another troublesome parasite is the chigger. 



Description. — -This parasite is scientifically known as the 

 Trombidium holosericeum and is minute in size, and hence 

 commonly known as the chicken mite. It varies in size up 

 to half the size of a common pin-head. Its body is oval in 

 shape, and varies from a light-yellow tinge in the young state 



