THE TSETSE FLY, GLOSSINA PALPALJS. 235 



a fitting for the hypopygium — probably homologising with this 

 part, as it seems a continuation of it. 



Between the forcipes superiores and the laminae superiores is 

 the penis, appendix interna, or adminiculum — a complex structure 

 furnished with paired hooks, inner claspers, or forcipes interiores, 

 paired palpi, genital palpi, and a single posterior hook known as 

 the tittilator. In addition to these, an organ of spatulate form, 

 the apodeme, is usually to be found situated below the whole of 

 the parts. 



The genitalia of G'lossina palpalis are sub-hamate ; the hypo- 

 pygium is large and bulbous, and armed with two strong outer 

 claspers (forcipes superiores) at its extremity (Plate 15, Figs. 2 

 and 5). The whole organ is hinged on to the penultimate segment 

 of the abdomen, which has attached to it an arched plate (lamina 

 superior), against which the hooks rest when the hypopygium is 

 turned under. The forcipes inferiores are absent or rudimentary,, 

 represented by a membrane with two rows of hairs (Fig. 5). 



Within the hypopygium is a second enclosing wall of chitin. 

 When seen from above it has somewhat the shape of an arch, the 

 ends being away from the forcipes superiores and joining on to 

 a paired process connected with the adminiculum (Figs. 2 and 4). 



The sides of this wall have several thickenings or buttresses of 

 chitin. At the top the sides rise, ending in a short, strong, bent 

 rod which supports the curious structure, presently to be de- 

 scribed, situated on the top of the adminiculum ; this rod may 

 homologise with the tittilator. The penis or adminiculum is an 

 elaborate structure consisting of two rods, which fuse at their 

 bases into a plate, which seems fitted for the attachment of 

 muscles (Fig. 6). Between the fork of the rods is a curious club- 

 shaped organ of small size (Figs. 3, 4, and 6). It is probably 

 the atrophying remains of the central apodeme. 



At the upper part of the adminiculum is a blunt, hook-shaped 

 projection ; over the whole organ is spread a membrane, which 

 probably contains the spermatozoa in their passage through the 



Jourx. Q. M. C, Series II. — No. 57. 17 



