86 MEDICAL ENTOMOLOGY 



may be distinguished. Unfortunately this variability makes them very 

 difficult to study, and the homology of the parts has not yet been 

 determined with any exactitude, a circumstance which rendrs the adop- 

 tion of a satisfactory terminology very difficult. The same type of 

 apparatus is found in each genus, however, and the parts have been 

 successfully used, in the cases of Phlebototnus and Glossina, for the 

 differentiation of species. It is evident that a classification founded 

 on such definite morphological points is of much greater and more 

 permanent value than one founded upon mere surface markings and 

 colouration, which are not always constant for the species. 



The male external genitalia are referred to under the general term 

 hypopygium. They consist of a series of bilateral hooks or claws, 

 with which the male attaches itself to the female during coitus, and 

 a median set of structures which includes the penis and its sheath. 

 Usually there are two pairs of claw-like structures, which may be 

 either concealed within the abdomen when not in use or remain per- 

 manently outside ; these are termed the claspers. One pair of them, 

 usually the superior, is much larger than the other. The internal 

 structures lie between the claspers, and are provided with a muscular 

 mechanism by means of which the penis can be protruded at will 

 through its sheath ; the penis is connected with the seminal vescicles 

 by an ejaculatory duct. 



The external genitalia of the male Phlebotomus (Plate XVIII, fig. 4) 



have been described by Newstead and by Annandale. They consist 



of two pairs of claspers, a sub-median lamella, certain 



External Genitalia intermediate appendages, and all intromittent organ. 

 of Phlebotomus 



The superior claspers are dorsal in position, and 



form large and conspicuous objects at the end of the abdomen, thus 

 affording a character by which the sexes can be distinguished at a 

 glance. They are composed of two segments, which, in the position 

 of rest, are acutely flexed on one another, so that the terminal one 

 comes to lie in the vertical axis of the body. The proximal segment 

 is larger and stouter than the distal ; both are covered with a dense 

 coating of hairs, and the terminal segment is provided with a series 

 of large spines at the apex, to which Newstead attaches a specific value. 

 The inferior claspers are smaller, and are unsegmented ; they are placed 

 ventrally and oppose the superior claspers, reaching as far as or beyond 

 the distal end of the first joint of the latter. They may bear spines 

 at the distal end. The sub-median lamellae are thin leaf-like structures, 

 which lie . between the inferior claspers, and are therefore only seen 



