DISEASES Ob- POULTRY. 177 



of lice which live upon them alone, and there are but 

 comparatively few kinds of lice which live upon two 

 or more species of birds. We may, consequently, 

 favor the multiplication of lice by making the con- 

 ditions favorable for them, but we can not produce lice 

 where none exist. 



The conditions which favor the multiplication of 

 lice and other external parasites are found partly in 

 the birds and partly in the surroundings. Unhealthy 

 or unthrifty birds, or those which 

 from any cause lack strength and 

 vigor are most subject to the at- 

 tacks of such parasites, and may 

 be found literally covered with 

 them when other members of the 

 flock are comparatively free from 

 their attacks. For similar rea- 

 sons some varieties of birds are 

 much more likely to be infested 

 with vermin under the same con - 

 ditions than are others. There YigAL—Coniodes dissimiim. 

 are birds so strong, healthy and °^ ^' 



vigorous that lice can not thrive upon them. Exer- 

 cise, proper feeding, pure air, all have a tendency to 

 keep the birds in a condition unfavorable to the ex- 

 istence of the parasites. On the other hand accumu - 

 lations of manure and filth, close confinement of the 

 birds, lack of dusting places, buildings with crevices 

 in which the insects may hide, and damp, dark and 

 badly ventilated houses are conditions which favor the 

 parasites and lead to their rapid development. 



The poultry -yard may be kept practically free from 

 these insect pests, but there is always a liability of 

 their introduction with purchased fowls or with birds 



