234 ENTOMOLOGY 



species of bird, though in the majority of cases this is not so. Several 

 mallophagan species often infest a single bird; thus nine species occur 

 on the hen, and no less than twelve species, representing five genera, on 

 the American coot. These parasites spread by contact from male to 

 female, from old to young, and from one bird to another when the birds 

 are gregarious. When a single species of bird louse occurs on two or 

 more hosts, these are almost always closely allied, and Kellogg has sug- 

 gested the interesting possibility that such a species has persisted un- 

 changed from a host which was the common ancestor of the two or more 

 present hosts. Mallophaga are not altogether limited to birds, how- 

 ever, for they may be found on cattle, horses, cats, dogs, arid some other 

 mammals; Kellogg records eighteen species from fifteen species of mam- 

 mals. These biting lice feed, not upon blood, but upon epidermal 

 cells and portions of feathers or hairs. They have flat tough bodies 

 (Fig. 18), with no traces of wings, and a large head with only simple eyes ; 

 the eggs are glued to feathers or hairs. 



Mammals only are infested by the sucking lice, or Pediculidae. 

 These (Fig. 24) have a large oval or rounded abdomen, no wings, a 

 small head, minute simple eyes or none, and claws that are adapted to 

 clutch hairs; the eggs are glued to hairs. Sucking lice affect horses, 

 cattle, sheep, dogs, monkeys, seals, elephants, etc., and man is para- 

 sitized by three species, namely, the head louse (Pediculus humanus 

 capitis), the body louse (Pediculus humanus corporis), and the crab 

 louse (Phthirius pubis) . 



An anomalous beetle, Platypsyllus castoris, occurs throughout North 

 America and also in Europe as a parasite of the beaver. 



The fleas, allied to Diptera but constituting a distinct order (Siphon- 

 aptera), are familiar parasites of chickens, cats, dogs and human beings. 

 These insects (Fig. 32) are well adapted by their laterally compressed 

 bodies for slipping about among hairs, and their saltatory powers and 

 general elusiveness are well known. Their wings are reduced to mere 

 rudiments, their eyes when present are minute and simple and their 

 mouth parts are suctorial. 



Among Diptera, there are a few external parasites, the best known 

 of which is the sheep tick (Melophagus ovinus), though several highly 

 interesting but little-studied forms are parasitic upon birds and bats. 



The larvae of the bot-flies (CEstridae) are common internal parasites 

 of mammals. The sheep bot-fly ((Estrus ovis) deposits her eggs or 

 larvae on the nostrils of sheep; the maggots develop in the frontal sinuses 

 of the host, causing vertigo or even death, and when full grown escape 



