THE TSETSE FLY, GLOSSINA PALPALIS. 237 



With regard to the central apodeme, already referred to, 

 I first observed this part in Scatophaga stercorcwia L. ; but I 

 was not able to assign to it any definite function. If it is 

 present in S. lutaria F., it is in a much altered form ; but it 

 is quite recognisable in Xorellia striolata Mg., another species of 

 the Cordiluridae. It is well marked, though relatively small 

 in size in Calliphora erythrocephala Mg., but larger in Ducffla 

 cornicina F. of the Muscidae. In the Lonchaeidae I have found 

 it in P allopter a ustulata Fin. In Xemopoda cylindrica F., of the 

 family Sepsidae, it is very long ; it is of the same shape in an 

 unidentified species of the same genus from Jersey, and it is also 

 evident in Diopsis apicalis Dal., the curious fly, with eyes on long 

 stalks, from Natal. In the Empidae it is marked in Empis 

 chioptera Fin., E. vitripennis Mg., Helara cilipes Mg., and 

 H. matrona Hal. In the Syrphidae it is present in Syritta 

 pipiens Deg. In Tipula oleracea L. the ejaculatory apparatus 

 is worked by a somewhat circular organ, to which are attached 

 three levers for the attachment of muscles. In Pachyrrhina 

 maculosa Mg. is a similar arrangement, but in place of the 

 circular organ is a spatulate lever obviously homologous with 

 those already enumerated. In a South Australian Asylid, at 

 present unidentified, is the same apodeme, working at the base 

 of a very short adminiculum, the ejaculatory apparatus being in 

 the lower part of the organ. From this I conclude that the 

 function of this lever, when present, is the same as in T. oleracea. 



In G. palpalis there is a wide departure from the normal type. 

 The base of the penis, having separated from its sheath and 

 developing into a lever, has probably usurped the functions of 

 the apodeme, which has become reduced to a mere rudiment. 

 The size of the parts has but little bearing on the points likely 

 to be raised by a discussion on these genitalia; but as no descrip- 

 tion can be considered complete without some reference to it, 

 I may say that the double rods of the penis (Fig. -4) are T V of an 

 inch or 1494116 mm. long. 



