LICE WHICH AFFECT DOMESTIC ANIMALS 331 



badly infested early in the winter, some will have a few lice on them, and 

 others will seem to be free from them. 



The degree of dryness of the skin is often closely related to the num- 

 bers of lice on the different cows. When cows are not in good physical 

 condition this results in a lack of natural oiliness of skin and makes con- 

 ditions ideal for lice to increase. It will be noted that the variation in 

 the numbers of lice on cows varies with the breed; that Holsteins are 

 notably among the most infested; that Ayrshires and Guernseys are 

 intermediate; and that Jerseys are not so badly infested. Calves, which 

 have less oily skin than older stock, are more generally infested with lice. 



There is a marked difference in the season of the year when lice are 

 more numerous. The skin secretions are reduced in the winter and it is 

 then that the lice are most numerous. In the summer only a few can 

 be found. Certain cows in a herd will be infested early and will continue 

 infested through the winter. The fact that Holsteins, being usually 

 either black and white, or having the combined markings, make the lice 

 more conspicuous, seemed at first to offer a solution for the reason 

 why they have been generally conceded to be the most heavily infested 

 breed of cows. Considerable study has, however, borne out the fact 

 that this greater susceptibility is due to the general lack of skin secre- 

 tion of the breed. For these reasons, it is believed that not only should 

 we try to keep the stables clean, well lighted, and well ventilated, but 

 also keep the stock in good physical condition. The fact that the lack 

 of oiliness of skin tends toward lousiness indicates a logical control meas- 

 ure for these parasites. 



Cattle lice are by no means uniformly distributed over a cow, particu- 

 larly if they are of the sucking species. The upper portions of the neck, 

 shoulder tops or withers, escutcheon and the switch of the tail are usually 

 the parts that are infested with the largest numbers. 



The forehead, portions between the horns, and the throat are places 

 where the lice are next most likely to be found. It is these places, espe- 

 cially the upper portions of the neck and withers, that the dairymen 

 should watch for indications of their presence and it is to these places 

 that the insecticide or control measure should be applied most liberallj' 

 and most thoroughly. While the small red biting lice move about some- 

 what, the sucking lice remain stationary during the greater portion of the 

 time before reaching maturity, feeding continually. 



SUCKING LICE 



The short-nosed cattle louse, Haematopimbs eurysternus Nitzsch, is 

 the best known of the cattle lice. It is very broad and measures in the 



