FEMALE GENITALIA: DIPTERA 89 



which the abdomen is shortened, as in the Muscidae, and reaches its 

 highest development in those flies, such as Musca, which deposit 

 their eggs in a soft substance. In the Orthorraphic flies it consists 

 merely of some small plates of chitin, representing tergites and sternites 

 of suppressed segments, which are connected together by membrane, 

 and, in the resting condition, folded beneath the last visible segment 

 of the abdominal wall. In the Culicidae an ovipositor as such can 

 hardly be said to exist, but the terminal segments, much reduced in size, 

 are closely compressed and at the same time connected together by a 

 membrane loose enough to allow the plates to be extended on one another 

 when the eggs are being laid. In Tabanits (Plate XIV, fig. 4) there are 

 several suppressed plates under cover of the last segment, which are 

 similarly attached, and can be drawn out by dissection, disclosing a 

 simple ovipositor. The dorsal wall of this is formed by one broad 

 plate, the tergite of the eighth segment, two small lateral plates which 

 represent the tergites of the ninth and tenth segments divided into two 

 lateral halves, and two anal plates, which project at the end of the 

 abdomen, and represent the tergite of the eleventh segment similary 

 divided in the middle line. The ventral wall is formed by a single 

 plate of an irregularly quadrilateral shape, which may represent the 

 sternites of the corresponding segments fused together. The greater 

 flexibility of the dorsal wall allows the ovipositor to be bent downwards 

 when it is in use. 



In Musca and those of its allies with similar breeding habits the 

 ovipositor, when extended for use, is a tube equal in length to the 



rest of the abdomen, and of a diameter suitable for 



Ovipositor of 

 the accommodation of the egg. The membrane between Musca 



the segments is so much increased that the tube when 

 fully stretched owes at least half its length to the inter-segmental 

 membrane, and the segments themselves are membraneous except for 

 the small sclerites in the dorsal and ventral walls which remain to 

 represent the original tergites and sternites. The sixth, seventh and 

 eighth segments can be distinguished, and at the terminal end there 

 is a small pair of plates, one dorsal and one ventral, which correspond 

 to the tergite and sternite of the suppressed ninth segment. When in 

 repose each of these divisions of the tube fits inside the one anterior 

 to it, and the whole organ is retracted within the abdomen. When in 

 use it curves downwards and a little forwards under the abdomen of 

 the fly, and is in many species actually thrust into the dung or other 

 soft substance in which the fly is about to deposit its eggs. 

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