W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTEKA. 95 



of the Muscidae are thought to be such. This part, then, 

 may be a tactile, an auditory, or an olfactory organ in different 

 species, and it is probable that in many instances all three 

 senses are located, perhaps not exclusively, but in part, in the 

 antennae. Professor Packard* says that, "the ears of the 

 locusts are situated one on each side, on the basal joint of the 

 abdomen just behind the first abdominal spiracle. In Meconema 

 a European grasshopper, the auditory organs are on the fore- 

 tibiae." I shall show that I have found in several Empidae, 

 an organ in the same situation, the use of which I shall discuss 

 later. 



Without in any way calling in question Packard's conclusion 

 as to Meconema, I would observe that in one case, where a 

 structure on the fore-leg was thought to be an auditory organ, 

 this explanation was quite wrong. The combed process, 

 fringing a concavity of the fore- tibia of very many Hymenoptera, 

 is the instance alluded to. Mr. Frank Cheshire found that it 

 was used to clean the antennae, and it seems absolutely clear that 

 this is its proper function. 



Lieut.-Col. Yerbury, to whom I am indebted for several 

 specimens of the insect, has drawn my attention to the very 

 marked powers of smell of Gastrojihilus equi, L., one of the 

 Oestridae, or bot-flies. He tells me that his method of cap- 

 turing the insect was, on a sunny day, to take up a position 

 on the windward side of a cart-horse ; generalh^ after a short 

 time a bot-fly would come up on his leeward side ; often both 

 Col. Yerbury and the horse would hear the fly before they 

 saw it, and invariably the fly came up the wind, and was seen 

 first on the opposite side of the horse. This shows a very highly 

 developed sense of smell, equal to that of many of the mammalia, 

 or even greater if we compare the surfaces exposed. I therefore 

 made preparations of this insect, and examined every part of the 

 external anatomy with a view of finding special olfactory organs. 

 I used an excellent i-in. objective, which, working at an unusual 

 distance, affords great assistance to an entomologist. 



The result was negative for all parts except the antennae. 



I then examined these, comparing them with those on flies 



of about the same size. They were very distinctly larger than 



those of Helophilus penduhis, L., Thelaira nigripes, F., and 



* Texthooli of Entomology, pp. 288, 289, 



