External Parasites 209 



flock), or (6) when two hens occupy a nest together, or (c) 

 from mother to chick. They also pass indirectly from bird 

 to bird by crawling off one bird first on to the nesting material 

 and later on to another bird which uses the same nest. Sharp 

 has also observed several lice clinging to the body of a 

 fly parasitic upon chickens. Lice are so much more common 

 than the parasitic fly that it is probable that this insect 

 is of little real importance in the distribution of the lice. 



All the lice breed very rapidly. In 8 weeks the third 

 generation is mature and in this generation the estimated 

 number of the offspring of a single pair is 125,000 individuals. 

 It seems important to eradicate an infestation if possible 

 as soon as discovered. However, if kept under sanitary 

 conditions and furnished with plenty of attractive dust, 

 vigorous birds will hold external parasites in check. With 

 some attention to sick birds, setting hens and young chicks, 

 the parasites will give little trouble on a plant conducted 

 with due regard to the principles of hygiene and sanitation 

 (cf. Chapter II). 



Salmon ("Diseases of Poultry") says: "It should be re- 

 membered at all times that the external animal parasites 

 are the most common and frequent cause of trouble in 

 the poultry-yard and pigeon-cote. If the birds are not 

 thriving and conducting themselves satisfactorily, look 

 for these pests, take measures to repress them, and in 

 most cases the results will be surprising and gratifying. 

 When anything is the matter with a horse the maxim is 

 examine his feet, and when anything is found wrong with 

 poultry or other domesticated birds, the maxim should be 

 look for lice." 



Diagnosis. — Adult hens may harbor quite a number of 

 these parasites without showing any symptoms which indi- 

 cate their presence. If they are unthrifty and broody hens 

 leave their nests they should be examined for lice. The 



