DE. J. B. HICKS ON A NEW ORGAN IN INSECTS. 139 



in each of the halteres (in Mhingia for instance) is about 120 

 for each principal face, making for the three faces 360. 



Thus we find a nerve, the largest nerve except the optic, enter- 

 ing the halteres, where there are no muscles, therefore this nerve 

 must be one of sensation ; and I think it will be allowed that it 

 must be one of special sensation. 



But as there is also a nerve going to the base of the wings, we 

 might expect to find similar structures there, and we shall not be 

 disappointed ; for if we look on the subcostal nervure at the base, 

 we shall see a group of vesicles of a similar character to those on 

 the halteres, — not so beautifully arranged, but still very distinct, 

 as is clearly shown in the Tabanidce and some Muscce (fig. 5). 

 They extend in a single row some little distance up the nervure, 

 and are found on both sides of the nervure, but principally on 

 the upper side. 



These organs are not confined to the Diptera, but 1 believe 

 are to be found in all insects ; at least I have found them as far 

 as I have examined. They exist on both sides, but principally 

 on the upper side of the base of the subcostal nervure; on 

 the costal nerve in Hemiptera. Those on the second wing are 

 generally the largest in number and size ; but that, I suspect, is 

 determined by the size of the nerve proceeding to them. In 

 Moths they are very apparent, being greatest in the JSToctuce and 

 Bomlycidce. There are about 100 vesicles on the upper surface 

 of the posterior wing, and half that number beneath, besides some 

 few on the nervures. (See fig. 7 b.) In the Butterfly they are 

 smaller, but arranged in more definite groups, about three in 

 number. In Coleoptera and Neuroptera they are arranged in long 

 rows along the subcostal nerve ; they are more apparent in Co- 

 leoptera than in Neuroptera. In the Hymenoptera, for instance the 

 Bee, they are found in a rounded group of about forty on each 

 side (fig. 6 a). 



In a subsequent paper I hope to show a more extended analysis 

 of this structure in the different tribes of Insects. 



Now, what is the nature of these organs ? Are they organs of 

 smell, as suggested by Mr. Purkiss ? As the olfactory organ has 

 never yet been decided on, it seems to me not improbable that 

 they may be the organs of that sense ; for, first, it is not likely 

 that they should be the organ of hearing, as they are in constant 

 motion, and situated near the source of the hum of the wings, so 

 that other sounds would be drowned. 2ndly. It is not necessary 

 that the power of smell should be in the head. It is situated in 



