INSECT ENEMIES OF LIVE STOCK 189 



environment of feathers, skin, and temperature, in which 

 the lice dwell, remains unchanged. 



Although the Mallophaga are provided with biting 

 mouths, they do not, according to most observers, suck 

 blood, but sustain themselves on skin scales and bits of 

 feathers. One species, however, lives inside the pouch of 

 the Calif or nian brown pelican, clinging to the pouch walls 

 by its mandibles. What form of nutriment is taken up, 

 in this case, is a debatable point. All the bird lice are pro- 

 vided with sharp claws, and, as they are constantly on the 

 move, they set up irritation in the skin of their host and 

 have an injurious effect on its general health. Sometimes 

 the infestation may be serious enough to set up pruritis, 

 an intense skin irritation which is exceedingly weakening, 

 and, in laying hens, effectually reduces egg production. 

 Infested chicks become stunted and fail to make normal 

 growth, whilst failures in hatching are of frequent occur- 

 rence, because the sitting hen is rendered so restless that she 

 breaks many of her eggs. Despite this catalogue of woes 

 likely to befall the louse-infested hen, it must be clearly 

 understood that the parasites are not disease-carriers ; the 

 trouble which follows in their wake is purely superficial, 

 though none the less unpleasant for being so. 



Though the Mallophaga are known as bird lice, some 

 of them occur on mammals. They are hard, flattened, 

 simple-eyed insects, with strong legs, of which the first 

 two are short, and, after the manner of hands, are used to 

 convey food to the mouth. The female louse deposits its 

 eggs on the hairs and feathers of the host, and the young 

 insects, except for their relatively large heads, resemble 

 their parents, for they do not undergo complete meta- 

 morphosis, but grow by a series of moults into adults. 

 The death of the host is followed by the death of its 

 parasites, though they often attempt to reach another 

 host, as is shown by the fact that they crawl towards the 

 head. Being feather-eaters and not blood-suckers, it is 



