XIV 



Larvae : Are worm-like, whitish, consisting of fourteen 

 segments. They are about one-and-a-half by one-tenth 

 millimetres in size. They feed on organic refuse (?) and on 

 blood. In about eleven days they are full grown. 



Nymphs. — Have legs but are stationary. After the lapse 

 of eleven days the flea emerges (the evolution thus taking 

 about a month). 



Anatomy 



1. The head is small, not distinctly separated from the 

 body. 



2. The antennae are placed in fossae behind the eyes. 

 They consist of two basal segments, and a third of diverse 

 form irregularly segmented. The maxillary palpi must not 

 be mistaken for them. 



3. The mouth consists of (a) hypopharynx (the central 

 stylet) serrated above, tubular below ; (b) two serrated man- 

 dibles hollowed on their inner surfaces and forming with (a) a 

 gutter, along which the blood flows ; (c) a labium single for a 

 short distance, then bifurcating and forming two labial palps, 

 which form a sheath for the piercing organs (a) and (6) ; 

 {d) two maxillae having the form of expanded plates, each 

 bearing a four- jointed palpus. 



4. The thoracic segments, three in number, are separate. 

 The metanotum has a ' wing-like ' flap or epiphysis especially 

 well developed in the Sarcopsyllidae. 



5. Abdomen consisting of ten segments, overlapping ; 

 the dorsal and ventral portions not being united, and so 

 allowing of distension. The terminal segments are highly 

 specialized forming the genital apparatus. The sexes are 

 readily distinguished by this means (Vide Fig.) 



Capture of Fleas 



Small animals, such as rats, are best chloroformed in a box 

 with a glass top. The fleas are subsequently carefully brushed 

 out. The nests of small animals, such as mice, birds, etc., are 

 often a rich source of fleas. The nest should be put in a bag 

 for subsequent examination. For lifting the fleas use the tip 

 of a stiff feather dipped in spirit. Very careful manipulation 

 is necessary to avoid damaging bristles or spines. 



Identification of Fleas 

 The number of described species already approaches two 

 hundred. Consequently all that we can attempt here is to 

 indicate some points in the structure of fleas. The external 



