372 ME. WALTEE WESCHfi ON THE GENITALIA OF 



articulated to the tlieca. At the base of the penis is a sac surrounded by muscles, 

 which may be some form of ejaculatory apparatus. 



I have also made a few dissections and preparations in the Coleoptera, Lepidoptera, 

 and Hymenoptera, which show that the male genitalia, as might be expected, since 

 mouth and ail other parts agree, can be homologized on the scheme originally con- 

 structed from the organs in the Diptera. 



Coleoptera. — Lucamis cervus, Linn., has a long flagellum similar to that in the Ortalidae 

 (PI. 28. fig. 96). This starts from a bulb articulated to the penis, which is supported by 

 two apodemes. The ejaculatory duct can be traced to the bulb of the flagellum, and 

 has a structure similar to that on the part in Si/ritta p'piens. The whole organ is 

 swathed in several chitinous envelopes, probably representing segments of the abdomen, 

 and the theca, which immediately surrounds the penis, supports the forcipes interiores. 



Acil'ms sulcatns (Linn.), an aquatic insect, has the " titillator" much developed and 

 occupying its usual position. This part is also to be seen in a preparation of a land 

 beetle which I cannot satisfactorily identify. 



In Geotrtqjes stercorarius (Linn.) the theca is long and cylindrical ; it bears at its 

 extremity two articulated plates, the forcipes interiores ; through these protrudes a 

 sensory membrane, which envelops a chitinous structure ; this structure is extruded by 

 two slender apodemes. 



Necrophorus interrnptus, Stepli., is of the same type, but the forcipes interiores are 

 longer, and the apodemes cannot be recognized. 



Lepidoptera. — In the Lepidoptera the genitalia are mostly simple, often consisting of 

 only the forcipes superiores and a horny central penis; but in Arctia caja (Linn.), 

 which has a wide distribution, I find the forcipes superiores seemingly fused into a 

 single piece, the theca suj)porting a pair of forcij)es interiores and surrounding the base 

 of a cylindrical penis, with a membranous process running through it ; the membrane 

 having the triangular aculeations so common in Diptera and also to be found on the 

 genitalia of the drone in Apis mellifica. In Neuronia popularis a pair of apodemes can 

 be differentiated. 



Hymeiioptera. — A Saw-fly, Cimbex ariana, Kirby, has the hypopygium turned in 

 under tlie abdomen exactly as in Glossina ; the plate carries cerci and hairy organs, 

 representing the forcipes superiores and inferiores. It will be remembered that 

 G. palpalis has forcipes superiores and the remains of atrophied forcipes inferiores in an 

 identical situation. The theca surrounds the penis and bears the forcipes interiores and 

 the palpi genitalium ; but the penis in the Tenth redinidae consists of paired convoluted 

 valves, each supported by an apodeme, and the mechanism of the ejaculatory apparatus 

 (if one exists ?) is not obvious. I have found a similar penis in several species of 

 Nematus. 



I think it probable that an examination of a number of families in Insecta will yield 

 types closer to Diptera than those considered, but there appears nothing to guide the 

 enquirer to a particular genus or family. I now recur to my main argument, the 

 relationship between the mouth-parts and the genitalia. 



