ENTOMOLOGY

LICE WHICH AFFECT DOMESTIC ANIMALS 341nine months apart from the host. This seems f::xceptional as we havenever observed longevity to exceed three weeks. While specimens of licemay drop off with feathers, we find in the method of treatment which isdescribed below that no concern need be felt for the reinfestation of aflock from this source. It also appears that wild birds play very littlepart in the carrying of these pests. Of course it is possible that sparrowsor other birds intimately associated with domestic fowls might accidentallycarry a few specimens from one yard to another.Injury and Lossss.-It is difficult to weigh the loss produced by lice.It is generally believed by poultrymen that where they are at all abundantthey materially affect the development and egg production in fowls. Certainit is that young chicks are fI'equently killed by the attack of the headlouse and this also applies to young turkeys and ducks. Just how theinjury is produced is still a matter of debate. Since the lice do not suckblood it is generally believed that the injurious effects are produced bythe irritation caused by the gnawing and running about of the parasites.We have seen repeated instances of the rapid increase in weight of grownfowls after they have been freed of lice and experiments now under wayseem to indicate clearly that egg production -is markedly affected by evenmoderate infestations of lice. In addition to these adverse effects it hasalso been found that lice, especially when present in numbers, mutilatethe plumage of the fowls. This is of special importance in showbirds.While no disease has been demonstrated to be carried by poultrylice, it is not improbable that they may playa part in the transmissionof some maladies of fowls. They have been suspected of being concernedin the spread of the so-called chicken pox, or sore head, and favus.Methods' of Control.-While there are a number of insecticides whichare fairly satisfactory in reducing the number of lice on poultry, experimentscllrried out by Mr. H. P. Wood and the writer at Dallas, Texas,indicate that none of them are as satisfactory as sodium fluoride. Thecommercial grade ranging from 90 to 97 per cent N aF is used. This isa white powder readily soluble in water and with comparatively low toxiceffect on the higher animals. It has been found that one light applicationis sufficient to completely rid a fowl of all species of lice. The actionof the material is rather slow, especially when it is used in the dustform. Usually it takes ahQut four days for all lice to disappearfrom the feathers. Since the lice chew their food and since other parasiteswhich suck the blood from the host arc not destroyed to a largeextent, it is believed that the material acts largely as a stomach poison.Hatching of the eggs does not appear to be prevented but the young licesuccumb very soon after emerging from their shells.Sodium fluoride may be applied either as a powder or in solution.