POULTRY DISEASES AND THEIR TREATAIENT. 



133 



of great economic importance. Occasionally one or another of 

 the other species becomes sufficiently abvmdant to be of local 

 importance. The mites are small 8-legged animals related to 

 the spiders. Some of the mites parasitic on the fowl visit their 

 host only to feed, as the common red mite ; others remain on the 

 surface of the skin or on the feathers, as in the case of deplum- 

 ing scabies. Others live under the skin, causing deep-seated 

 skin diseases like scaly leg; still others find their way into the 

 internal regions of the body, living either on mucous membranes 

 like the air sac mite (p. no) or upon the connective tissue like 

 the connective tissue mite. 



Fig. 28. The common "red mite" of poultry, Dcriiiany- 

 ssus galliiiae, a, adult, d and e, young. (After 

 Osborn) . 



The most common and most injurious mite parasitic on fowls 

 is the common fowl mite or red mite, Dermanyssus gallincF. 

 These mites are present in almost every poultry house that is not 

 kept very clean. When they are present in large numbers they 

 are a serious pest. This mite is a little more than j4 millimeter 

 long. The female is a little larger than the male. When empty 

 Ihey are gray with dark spots, but usually they appear some 

 shade from yellow to dark red according to the amount of fowl's 

 blood they contain. They visit the fowls only to feed and spend 

 the rest of the time on the under sides of the roosts, in cracks 

 and crevices, under collections of droppings or other filth and 

 in the nesting material, especially if such material is dirty straw. 

 The mites breed in these places. They reproduce very rapidly, 

 especially in .spring and summer. The eggs are laid in con- 



