406 Transactions of the Society. 



Syrpiiid2E. — Sphazrophoria scripta L. has the outer edges of the 

 abdomen decidedly more thickly haired than the same part in 

 the male. 



Conopod^e. — C. quadrifasciata Deg. has a remarkable organ 

 which protrudes from the ventral side of the abdomen, and hangs 

 down anteriorly to the opening of the vagina. A microscopic 

 preparation shows an even more remarkable complexity ; pos- 

 teriorly to the opening of the vagina are two very powerful teeth 

 with levers attached to their bases. Opposite are two lobes studded 

 with blunt spines, and with sensory hairs on the extremities. 

 More anterior to this, and on the ventral part, is an area also 

 studded with blunt spines, but more densely, and arranged in 

 rows of 2, 3, 5, and 6. From this point begins the descent of the 

 organ alluded to, which is seen to be a hairy unpaired lobe, fur- 

 nished on the posterior side with short blunt spines more sparsely 

 distributed, and on the anterior surface with sharp hairs (plate VII. 

 figs. 14, 15). 



In C. fiavipes L. an even more striking appearance is seen, as 

 the " unpaired lobe " appears to have quite a point. In a prepared 

 specimen the vagina is found to be even more armed than in 

 C. quadrifasciata, as is also the posterior surface of the lobe and 

 the ventral space between. Posterior to the male genitalia of 

 the last-named species is a little shiny black knob ; this is a paired 

 organ homologous with the " forcipes superiores " of the ordinary 

 genitalia. This knob, when the whole hypopygium is turned in 

 under the abdomen of the female, comes in contact with the serrated 

 posterior surface of the " lobe " and is kept in position by it. That 

 being so, effective fertilisation would be greatly helped by the 

 " unpaired lobe," and it is easy to see that females possessing it, or 

 tending to vary in the direction of greater development, would 

 have an advantage over the simpler females, and, passing on the 

 character to their female offspring, produce these extraordinary 

 complications (plate VII. figs. 16, 17). 



Anthomyid/E. Pegomyia latitarsis Ztt. has the last joint of 

 the posterior tarsi enlarged, while the males are normal ; the 

 advantage of this to the possessor is not obvious. Pegomyia 

 bicolor W. has two very thickly haired patches, placed one behind 

 the other on the ventral side of the abdomen, close to the aper- 

 ture of the ovipositor. There are also two groups of eight spines 

 disposed laterally on each side of the posterior patches. 



Cordylurid^e. Norellia spinimana Fin. has a number of 

 blunt spines on the ventral side of the abdomen and below the 

 ovipositor. 



Sapromyzid^e. S. fasciata Fin. has on each side of the fourth 

 segment a patch of very fine bristles, highly chitinised and seated 

 on a curious corrugation of membrane ; S. apicalis Lw. has the 

 fine hair of the membrane, laterally on the lower part of the 



