INSECTA 189 



covered with numerous little thorns and points, between which are 

 single, long sense-hairs, each occupying a round, lighter space. In the 

 male, the lateral arms of the 9th dorsal splint are very much bent 

 towards the ventral ridge, and are continued as straight processes both 

 anteriorly and posteriorly. The two posterior processes bear each a 

 leaf-shaped appendage which is directed backwards, and the free edges 

 of which are set with bristles. This apparatus is employed during 

 copulation to attach the male to the female. The ventral splint of the 

 9fch segment, in the male, takes the form of a two-pronged fork, the 

 prongs of which run towards the dorsal ridge while the handle is 

 directed posteriorly. Between the two prongs is the penis, a chitinous 

 organ, spiral in shape, which is withdrawn into the abdomen. In the 

 female, both the ventral splint and the lateral arms of the dorsal splint 

 are of slight development only ; the former is closely covered with 

 bristles. 



The 10th segment is rudimentary ; upon it is the anus, and below 

 the anus the genital opening. 



The dorsal splints of the three thoracic segments are semi-circular 

 in shape, and cover the back and side of each segment. Upon each 

 side of the segment, ventrally of the dorsal splint, is a four-cornered 

 plate, the pleuron, to which the legs are attached. As the pleurons of 

 the 1st thoracic segment are directed forwards and lie under the head, 

 the 1st pair of legs appear to be attached to the head. The pleurons 

 of the 2nd and 3rd thoracic segments are divided by a longitudinal 

 ridge into anterior and posterior halves. The posterior portions of the 

 pleurons of the 3rd thoracic segment are prolonged backwards to the 

 abdomen, and have the appearance of rudimentary wings. 



The legs of the flea, like the body, are very much flattened. They 

 increase in length from front to back, and have the same number of 

 joints as in other Insecta. They differ, however, from those of other 

 members of the same group in the remarkable development of the 

 coxae or thigh-joints, which are as long as the femur and tibia, and 

 are even broader. The five-jointed tarsi, which terminate in two 

 claws, are also comparatively long. 



The flea differs from other Insecta, moreover, in possessing a larger 

 number of stigmata, of which there are three thoracic and seven 

 abdominal pairs. The abdominal stigmata are placed upon the lateral 

 surfaces of the 2nd to 8th segments. Two pairs of thoracic stigmata 

 are situated ventrally between the pleurons, while the third is placed 

 dorsally. The head, body segments, and legs are all thickly covered 

 with hairs and bristles, the arrangement of which has considerable 

 specific value. Bristle ridges (rows of thicker bristles) occasionally 

 occur, usually upon the head and thorax. 



The abdominal viscera may be obtained in the following manner : 

 The flea should be killed in chloroform and examined under the 



