1916] Life History of Pterodontia 317 



ventral plate, which is visible only in a lateral view (Fig. 7). 

 The pharyngeal plates seem to fuse and form a median tooth or 

 beaklike rostrum which is capable of being slightly protruded. 

 The thoracic and abdominal segments are strongly chitinized 

 and consist of distinct tergal and sternal plates. In newly 

 hatched larvae the body-plates and segments are quite closely 

 drawn together, but in specimens which were removed from 

 their hosts the segments were distended, the terga and sterna 

 being separated by a pleural membrane (Fig. 7). The dorsal 

 and ventral surfaces of the thorax and abdomen are elaborately 

 armed with long and short spines and broad chitinous scales. 

 The dorsal scales are broad and palmate, with nine to eleven 

 points (Figs. 13 and 14). On the dorsum they are limited to 

 the mesothoracic and metathoracic terga, the remaining seg- 

 ments being armed with both long and short spines. There are 

 also a number of minute, round, clear spots, which occur only 

 on the terga. On the venter, the scales occur on all of the sterna 

 except the prothoracic and caudal segments. On the sterna of 

 the second and third thoracic segments and the first abdominal 

 segment the scales are broad and have seven points or digits; 

 the remaining segments are armed with smaller scales which for 

 the most part are three, five, and seven pointed. The scales 

 are firmly set into the body-wall through a funnellike opening 

 (Fig. 16). The caudal end of the eighth abdominal segment is 

 membranous and prolonged', forming a disk or sucker which 

 serves for attachment. On each side of the caudal disk is a 

 long, stiff, spring-bristle which is used in leaping. Spiracles 

 seem to be wanting. On the caudal margin of the eighth 

 abdominal terga are two crescentic areas which resemble 

 spiracles. These, however, are notches in which the caudal 

 setae, or spring-bristles, rest when the larva stands erect on its 

 attachment disk. 



HABITS OF THE LARVA. 



The young larvae are very active, particularly at night when 

 they are in almost constant action. Locomotion is accomplished 

 in several ways. There is a looping movement accomplished b}^ 

 attaching first the head and then the attachment disk in a 

 manner similar to that of a leech. A second method, that of 

 leaping, is effected by the larva standing erect on the attach- 

 ment disk with the spring-bristles bent at right angles to the 



