SYNOPSES OF NORTH AMERICAN 

 INVERTEBRATES. 



XIX. The Tri. 



The genus Trichodectes, the only genus of the family Tricho- 

 dectidae, is one of the two genera of the order Mallophaga 

 which are found on mammals. From the other genus, Gyro- 

 pus, Trichodectes is distinguished by the fact that its members 

 have a three-jointed antenna. The order Mallophaga has been 

 divided by Piaget ('80) into two families, the family Liothe- 

 idas and the family Philopteridae — the two being distinguished 

 by the character of the legs which are modified either for run- 

 ning (the former) or for clasping (the latter). Kellogg ('99) has 

 separated the genus Trichodectes from the Philopteridae by the 

 erection of the family Trichodectidze which he attributes to 

 Burmeister. His authority for this attribution is not evident. 

 Of the 48 species in the genus, 18 are considered here as hav- 

 ing been taken on North American Mammals. 



The species of Trichodectes are distinguished from one another 

 by such characters as the size and shape of the antennae, the 

 character of the setae, or hairs that clothe the body, the shape of 

 the thorax, the genitalia of both male and female, etc. In the 

 present paper, at the suggestion of Prof. Herbert Osborn, much 

 attention has been paid to the so-called "abdominal appendages" 

 of Piaget. This organ, for it is all one organ, is a growth of the 

 posterior ventral edge of the antepenultimate segment of the 

 abdomen, in the female. The extension grows backward, under- 

 lying the major portion of the last abdominal segment and grow- 

 ing upward at the sides to reach the level of the tergum of that 

 segment. The median portion of the extension, however, does 

 not grow very far backward and the result is the formation of 



