96 



W. WESCHE OX SOME NEW SEXSE-ORGAXS IN DIPTERA. 



CalUphora erythrocephala, Mg., and about the same size as- 

 Echinomyia /era, L. I have made an exact comparative 

 measurement, by drawing these antennae with squares in the 

 eye-piece of the microscope, and the result will be seen on Fig. 1, 

 below. Further, I found on the third joint of the antennae of 

 G. equi a larger number of sense-pits than on any of the flies 

 mentioned, and of a different structure. When I say sense-pits 

 I do not mean the minute perforations, 17,000 of which are said 

 to be on the antennae of the blow-fly, but a much larger and 

 more evident structure. This, which I have illustrated on 

 Plate 7, Figs. 4, 6, 7, is, owing to the diffraction produced by 



Fig. 1. — Antennae of Diptera. 



1. Helqphilus pcndulus, L. 



2. Gastrophilus equi, F. 



3. Echinomyia f era, L. 



4. Thelaira nigripes, P. 



5. CalUphora erythrocephala, Mg. 

 G. Stratiomys chameleon, L. 



the different layers, very difficult to make out ; without a 

 powerful sub-stage condenser, and strong illumination, the details 

 are invisible, and even with them the short rods or pegs on the 

 membrane do not show, but take the appearance show in Fig. 6. 

 Owing to one of the larger pits being on a fractured edge, I 

 was able to see these short rods and indicate them in my 

 diagram. The structure then consists (a) of a large number 

 of hairs which are on the outer surface ; (b) under these are 



