6lO THE AMERICAN NATURALIST. [Vol. XXXVII. 



two lateral flaps as can be seen in the figures. Dorsally it has 

 the appearance of forming a prominent curved hook at either side. 

 Much variation in this organ in the several species was found and 

 its general shape, together with the presence or absence of setae 

 on it afford excellent criteria for the separation of species. The 

 function of the abdominal appendage is partly in clinging to the 

 hairs of the host but more especially in the adjustment of the 

 eggs to the hairs. 



A word may be said concerning the general habits of these 

 insects. Their food consists of scales and epidermal excretions 

 from the host. The mouth-parts are fitted for biting and the 

 mandibles are well developed. They cling to the hairs of the 

 host by means of the mandibles, which are set at the posterior 

 end of a clypeal groove running longitudinally along the ventral 

 side of the head, into which groove may be fitted a hair and this 

 then grasped by the mandibles. It is probable that the sides of 

 the groove are capable of being closed down over the hair and 

 thus anchor the Mallophagan to the host, without the assistance 

 of the mandibles. The legs, also, assist in holding the insect to 

 the hair. The office of the abdominal appendage has been men- 

 tioned. The eggs are often seen in the body of the specimen. 

 There is a well-developed lid fitting over a chitinous capsule. 

 The capsule is glued to a hair and development occurs there, 

 the lid being shoved off at the emergence of the larva. Most 

 of the species are confined to one species of host, although 

 exceptions are met with. 



Only those species known to occur in North America are con- 

 sidered here. It is hoped that by the aid of the keys, the 

 figures and the descriptions, any member of the group in the 

 region defined may be identified, even if the host is not known. 

 The characters in the key are given in the main for either sex and 

 none of these characters are difficult of examination. A ready 

 method of preparation is to boil a few minutes in a solution of 

 potassic hydrate in water, clear in carbolic acid and mount in 

 balsam. ' 



No claim to completeness is made for this paper, for it is 

 improbable that it includes all the species to be found on North 

 American mammals. Doubtless there are species imported from 

 Europe that have thus far escaped our notice. 



