MICROSCOPIC OBJECTS. 80 



Fig. 159. Pigeon's Flea, female (Pulex columbse), x 15. 

 Order Aphaniptera. 



The different species of Fleas are chiefly distinguished from 

 each other by the different lengths of the joints of the leg and 

 tarsus. The following is the description of the order : 

 1 ' Wingless ; metamorphosis complete ; mouth suctorial ; ros- 

 trum composed of two serrated laminae and a thin suctorial 

 seta (see fig. 162), included in a jointed two-valved sheath." 

 The description of the species shown in the drawing is as 

 follows : " Prothorax with a pectinate fringe, none upon the 

 abdomen ; antennae of male erect, those of the female lying 

 in the depression." The abdomen of the female Flea generally 

 has nine segments. 



Most Fleas require to be macerated in the potassa for two 

 or three days, then to be pressed between glass slips so as to 

 remove part of the internal matter, replace them in the potassa 

 for a short time, when the rest of the contents will soon come 

 out under pressure ; dry, soak in turpentine until transparent 

 and mount in balsam as usual. 



Fig. 160. Mouse's Flea, male (Pulex muris), x 40. 



The general outline of the male Fleas seems quite different 

 from that of the females. Instead of the abdomen being in 

 a line with the head and thorax, it is turned up as if the 

 insect had been bent. The male insect has also erect 

 antennae (see drawing), and in the posterior legs the first 

 joint of the leg, called the coxa, is rather larger than is com- 

 monly found in other species ; and in the anterior and middle 

 legs the last joint of the tarsus is also large. 



The method of mounting is the same as in the preceding 

 description, only that the species, being much smaller, requires 

 less time in the potassa. 



