REPRODUCTIVE ORGANS: MELOPHAGUS 145 



entomologists. A very full account of the reproductive organs of Meloph- 

 agus has been written by Pratt. The conditions in Hippobosca are very 

 similar, and both resemble Glossina in the essential features, the 

 similarity forming a good example of convergent development. The 

 fact that Glossina is pupiparous does not, of course, indicate any direct 

 connection by descent between that genus and the Pupipara ; the latter 

 form a class by themselves, and are only distantly related to the 

 Muscidae. 



In Melophagus (Plate XXX), the ovaries are arranged on the same 

 plan as those of Glossina, but there are two ovarioles in each ovary 



instead of one. The same alternation in the produc- 



- , . , . . . , . Melophagus 



tion of the eggs is observed, but it is in this case a 



little more complicated, for not only do the ovaries alternate, but also the 

 ovarioles in each ovary, so that only every fourth larva is produced from 

 any given ovarian tube. The peritoneal coat of the ovary is much 

 thicker than in most Diptera, and presents some remarkable peculiarities 

 which have been described in detail by Pratt. 



The oviducts present a striking feature, not found in any other 

 Diptera, namely, the transformation of a part to form the recep- 

 taculum seminis. Each oviduct is short, and joins its fellow of the 

 opposite side to form a slight dilatation in the middle line near the 

 point at which the milk glands enter the cavity of the uterus, and it is 

 here that the sperms are found in the fertilized female. In the virgin 

 female the oviducts are not in line with the uterus as is usually the 

 case, but join it at a right angle, that is to say, they are more or less 

 perpendicular to the long axis of the body. When gestation is advanced 

 the angle becomes very acute as the anterior end of the uterus passes 

 forward with the growth in length of the larva. 



The uterus is broad, and occupies a considerable proportion of the 

 space within the abdomen, crowding the other viscera forwards when it 

 becomes enlarged. It is compressed dorso-ventrally, and is held in 

 position by large tracheae and muscles which run between it and the 

 abdominal wall, as in Glossina. The wall is composed of a thick inter- 

 lacing network of muscle fibres, internal to which there is the usual 

 chitinous intima. In the lower part of the cavity the intima is thick, 

 and is in continuity with, and of the same appearance as, the integument, 

 of which the lower part of the uterus and the vagina are evident 

 invaginations. In the upper part of the cavity the chitinous intima 

 is very thin, and is thrown into numerous folds when the lumen is 

 empty. The young larva is retained in this anterior portion for the 

 19 



