OF WASHINGTON. 115 



from the tubes and pores and other drops about to exude. Mr. 

 Pergande also informed him that in the case of those gall-mak 

 ing aphides in which no tubes or corresponding pores have been 

 discovered he had noticed drops of liquid in the galls which 

 must have come from the anus. 



The matter was discussed by several of the members present 

 and the consensus of opinion was to the effect that while liquid 

 is excreted from the anus yet it is excreted also from the 

 nectaries, and many of the members stated that they had 

 observed the fluid coming from the nectaries. 



Mr. Knab exhibited the volume for the year 1760 of the 

 French journal " Memoires de Mathematique et de Physique," 

 and called attention to an article published therein describing 

 the copulation of mosquitoes. The observations there recorded 

 were made by the commanding officer of a ship in passage from 

 India around the Cape of Good Hop'e, and from the description 

 of the act it was now possible to recognize the species involved 

 as Stegomyia calopus. The copulation was observed after the 

 vessel had been on its way some months and had rounded the 

 Cape, and after storms, indicating that the mosquitoes were 

 breeding on the vessel. The act took place in flight, but there 

 was no swarm and the sexes faced each other and clasped each 

 . other with their claws. This agreed with what is now known 

 of the habits of Stegomyia. Mr. Knab stated that the mosqui 

 toes recorded in this article as very abundant on board the vessel 

 early in the voyage were probably not Stegomyia but Culex, 

 and these no doubt perished, while those seen abundantly later, 

 and whose copulation was observed, were Stegomyia and were 

 undoubtedly bred on board the vessel. Mr. Knab pointed out 

 that there are two styles of copulation among mosquitoes and 

 these are correlated with the structure of the claws of the 

 female; the mosquitoes which copulate as described for 

 Stegomyia have toothed claws in the female, while those in 

 which there is a swarm of males into which the female flies 

 and where the sexes are joined end to end and facing in oppo 

 site directions, in the fashion of the Tipulidse or crane-flies, 

 have simple claws in the female. This character of the toothed 

 or simple claws is not one which has any importance in classi- 



