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ENTOMOLOGY FOR MEDICAL OFFICERS 



but is generally flattened and broadly impacted or sunk 

 against the thorax. The antennae are composed of a single 

 segment, which is sunk in a pit on either side of the mouth, 

 and bears a free bristle or a tuft of long hairs. The palpi 

 are coarse and somewhat curved, and form a loose sheath for 

 the proboscis when it is protruded. The proboscis, which is 

 retractile, is much like that of Glossina, the labium consisting 

 of a bulbous base and a slender shaft which forms a sheath 

 for the acicular epipharynx and the filiform hypopharynx — 

 these as in the Muscidea being the only mouth-parts, besides 

 the palpi already mentioned, that are present. The thorax 



Fio. 73.— Nycteribiid Fly from " Flying-fox " Bat. 



is flattened and strongly chitinised, its sterna being broad. 

 The legs are, usually, not much elongated, but are stout and 

 end in heavy and powerful claws ; these have the heel almost 

 as prominent as the tip, and sometimes have a third cusp 

 near the heel. The wings in some species are well developed, 

 and have a venation quite like that of the Muscidea ; in other 

 cases the veins are incomplete and are a good deal crowded 

 in the antero-internal part of the wing ; in other cases again 

 they are narrow, or short and narrow (vestigial) ; in Lipoptena 

 they are, as the name implies, caducous, and in the " sheep- 

 tick " {Melophagus) they are entirely wanting. The abdomen 

 is a tough sack with no distinct segmentation. 



The HippoboscidcB are to be regarded as Muscidea nicely 



