244 



GLOSSINA 



[CH. 



second and third segments a curious sense-organ, consisting 

 of a number of sacs lined with sensory epithehum and opening 

 to the exterior by a well-marked pore on the inner surface of 

 the third segment. From the structure of this organ it is 

 supposed to be auditory in function. The arista of the antenna 

 is three jointed, the first two joints being very small, the terminal 

 one broad and compressed, and feathered on its upper side 

 with about 22 or 23 fine branching hairs. 



The eyes are large and in both sexes are well separated ; 

 the anterior facets towards the inner margin are much larger 

 than those behind. 



Fig. 62. Comparative morphology of the proboscis oi'Glossina (I), Melo- 

 phagus (II) and Stomoxys (III). 



B, proboscis bulb ; G.S., common salivary duct ; Hyp., hypopharynx ; 

 L., labellae ; Lab., upper lip (labium) ; L. inf., lower lip. I, Glossina 

 palpalis ; II, Melophagus ovinus; 1\\, Stomoxys calcitrans ; X35. (After 

 Roubaud.) 



The horizontally projecting proboscis is strongly chitinized 

 and consists of a bulbous base contracting to a long and very 

 slender shaft. The base of the proboscis, or proboscis bulb, is 

 surrounded posteriorly by a fold of skin forming the hind-wall 

 of the buccal cavity. The proboscis is grooved dorsally to 



