52 THE extomoi.ogist's 1:KC0I!|i. 



young insects resemble the parents in ull essential characters, the 

 absence or incompleteness of the abdominal markings being the chief 

 point of difterence ; the chitinization of the plates makes the 

 insects darker as they get older, but the number of moults is not yet 

 known for any species. 



The food of the Mallophacja has formed the subject of consider- 

 able study, and it has been concluded that the conspicuous large, 

 dark, pear-shaped blotch in the abdomen, found in a majority of 

 individuals examined, is the crop and its contents, the latter composed 

 of hair, feathers, epidermal scales, and not blood. The dark colour, 

 of course, is most distinct directly after a full meal and later, after 

 digestion, is wanting. Blood has occasionally been found in the 

 crop ; and Kellogg describes at length the peculiar habit of Menniitm 

 titan var. luifctris, which is parasitic on the Californian Brown Pelican 

 {r<ifcanus califonticus), and is found commonly clinging to the inner 

 surface of the gular pouch. The clinging is accomplished by the use 

 of the numdibles, which are inserted in the skin of the pouch, and 

 the insects appear, when discovered, to be always firmly lodged. 

 Some effective clinging is, of course, necessary to prevent them being 

 carried away by the water taken into the mouth when feeding. In 

 several instances Kellogg noticed that a small region surrounding the 

 parasites was raw and bloody, biit he is inclined to think that their 

 food consisted of the epidermal scales of the inner wall of the pouch. 



The abundance of certain species, like ^[nutjnm pall id nm, on 

 domestic poultry, causes much inconvenience to the hosts, owing to 

 the irritation set up by the sharp-clawed feet of the parasites. On the 

 death of the host, the parasites remaining on the body die, and 

 Kellogg considers this is due to the loss of heat, since it cannot be due 

 to lack of food. It appears remarkable that those species which infest 

 swimming and diving birds are not furnished with special contrivances 

 for their mode of life, but, living as they do at the roots of the feathers, 

 where water never penetrates, such special contrivances are not 

 necessary. 



Although the Mallnphatja rarely pass from the host's body, yet 

 migration is accomplished in many species, without doubt. This may 

 easily take place among gregarious birds and mammals, or amongst 

 others at the breeding season. In the case of birds, gulls, etc., where 

 difterent species live gregariously, purasites can pass from one species 

 of bird to another, and hence the same species of insect may occasion- 

 ally be parasitic on different birds. 



But when the same insect is parasitic on two birds , which are 

 respectively confined to the New and Old Worlds, explanation is 

 difficult. Yet Kellogg mentions twenty-two different species which 

 have been described as parasitic on purely Old World birds, and which 

 he has found on other birds in the New World. I'hus he has found 

 Xirnnis si(/HatHs and X pilcus on the American Avocet, although they 

 were originally described from specimens taken on the European 

 Avocet. The meeting of these two birds is practically im- 

 possible, and the only reasonable explanation is that the parasitic 

 species have, in these instances, persisted unchanged from the common 

 ancestor of the two allied bird-species, now so completely separated. 

 As Kellogg points out in such cases — " the parasites have remained 

 practically unaffected by the conditions which have produced the 



