IN THE ANTENNyl5: AND PALPI OF DIPTERA. 49 



Text-fig. 18 shows a drawing of a portion of a transverse 

 section of Pcesilohothrits nobilitaius L. Two distinct kinds of pro- 

 cesses are present, large finger-sbaped processes scattered in large 

 numbers on tbe surface, and a smaller kind broad at the base and 

 tapering to a fine point. Turning to the palp, tliere are again 

 no pits and only one type of sensory process, this is in the shape 

 of a curved finger. In BoUchopus hrevipennis Meig., the sensory 

 apparatus was very similar. 



OYOLORHAPHA. ASCHIZA. 



PiPUNCULIDiE. 



I ha.ve not had the opportunity of examining this group, but 

 Wesche (5) describes Pi2nmcnlus zo7iatus as having small and 

 characterless antenna? but a well-marked sense-organ in the tip 

 of each palp. 



Syrpiiid^ (Text-figs. 19-27). 



This is by far the most interesting family of all the Diptera, 

 so far as the sense-pits are concerned. The Syrphidaj show an 

 enormous specialisation in the shape and complication of their 



Text-figure 19. 



Part of a trausvevse section tlivougli the antenna of Syrphus sp. X 980. 



sense-pits, and the pits in different species of the family show 

 a wide difierentiation. All sensory processes and sense-pits are 

 confined to the anteuna3, none being present in the palpi, so far 

 as could be seen. Text-fig. 19, part of a transverse section of the 

 antenna of Syiyhus sp.. shows a somewhat deeply sunken pit 

 lined at each side with stiff chitinous hairs ; at the base are two 

 bottle- shaped processes. 



Proc. ZooL. Soc— 1919, No. IV. 4 



