ORDER MALLOPHAGA 



751 



glands may be present or absent, and the testes may number four to six and 

 the egg tubes three to five. 



Life-History. — Owing to the fact that these parasites die in a few hours 

 to seven days if removed from the body of the host, and also in a few days if 

 the host which they do not leave is killed or dies, the life-story of not a single 

 species has so far been completely worked out. It is, however, known that 

 the eggs are fastened to the hairs or feathers of the host, and that the young 

 when hatched are like the parents, but smaller, paler, and without characteristic 

 skin markings ; they attain their adult characters without metamorphosis. 



They run freely about the host, feed upon hairs and feathers, and very rarely 

 upon dried blood, and usually pass from bird to bird or animal to animal by 

 contact, being rarely found away from the host, which they probably slightly 

 irritate, because birds are seen to be constantly cleaning their feathers. They 

 have been found to be parasitic on about 100 species of mammals, representing 

 48 genera, 24 families, and 5 orders, and 1,100 bird species, or 33 orders of 

 birds out of a total of 35 orders. 



Classification. — The principal factor which has influenced the evolution 

 of this curious group of animals is isolation, each host being, according to 

 Kellogg, like a small island, so that each species is made up of many dislocated 

 small groups, and this is why each species has to be given a very flexible 

 description, and why many varieties might be made from one species. This 

 condition of life is opposed to producing larger variations, which might be 

 used to make genera and families, and the life conditions of many of the species 

 are very similar. Hence varietal specific distinctions are many, and generic 

 and family few. 



Hence some 1,500 species are known, which can be divided into two sub- 

 orders, each 4 families and 27 genera. The mammalia-infesting families are 

 only two in number, the Gyopididae and Trichodechitidae, characterized by 

 having two-clawed members, and each of those families by only one genus. 

 The bird-infesting families are also two in number, and have respectively 15 

 and 10 genera. 



The following table gives the differentiation of the suborders' families: — 



SUBORDER i: ISCHNOCERA Kellogg, 1896. 



Antennae exposed, filiform, three- or five-segmented, no maxillary palpi, 

 mandibles vertical, crop with sac-like diverticula, ingluvial glands present, 

 testes four, egg tubes five. 



A. Antennae three-jointed, tarsi one claw. Habitat, mammals — 



TrichodectidcB. 



B. Antennae five- jointed, tarsi two claws. Habitat, birds — PhiloptevidcB . 



SUBORDER 2; AMBYCERA Kellogg, 1896. 



Antennae concealed, clavate or capitate, four-segmented, maxillary palpi 

 present, mandibles horizontal, crop single, ingluvial glands absent, testes 

 six, egg tubes three to five. 



A. Tarsi with one claw. Habitat, mammals — GyropidcB. 



B. Tarsi with two claws. Habitat, birds — Liotheidcs. 



The genera parasitic on mammals may be recognized as follows: — 



■ SUBORDER ISCHNOCERA Kellogg, 1896. 

 Family Trichodectid^ Burmeister, 1835. 

 This family contains only one genus, THchodectes Nitzsch, 181 8, which is 

 parasitic on mammals and has tarsi with only one claw. 



SUBORDER AMBYCERA Kellogg, 1896. 

 Family Gyropidje Burmeister, 1835. 

 This family contains only one genus, Gyropus Nitzsch, 181 8, parasitic on 

 mammals and with tarsi armed with only one claw. 



