812 



MR. J. O, H. FREW ON THE L4RA'AL 



the ])ostei'ioi' half of eaoh abdoininal segment. There is a row 

 behind tlie anus, and their presence makes it practically certain 

 that what in this and the other larvne described here (see Chlorops 

 above) I have called the ninth abdominal segment really is a 

 separate segment. 



C&phalo-Pharyiigeal Skeleton. (Text-fig. IG.) 



This is of the same general type as that of Chlorops, and the 

 dilierences of detail can be made out from the figures. The most 

 striking difference is perhaps the presence of a median ventral 



Text-figure 16. 



0-2 mm. 



M. nigriventris. Lateral view of ceplialo-pharyiigeal sclerites. 



piece. This plate also occurs in Balioptera comhinata, where its 

 relations with the neighbouring parts are more easily made out 

 (see below). 



Tracheal System. 



The anterior stigmnta are of the usumI branching type and are 

 situated near the posterior margin of the first body-segment, 

 slightly dorsal to the mid-lateral line. The branches are ex- 

 tremely short and project very little from the body-surface 

 (text-iig. 17). 



The posterior stigmata (text-fig. 18) are, as already mentioned, 

 sessile and not at the apex of a, stigmatic papilla; there is no 

 stigmatic plate and each of the three openings projects very 

 slightly above the body-surface. Four pairs of branching hairs 

 arise, as sliown in the figure. 



The arrangement of the tr-acheal trunks aiid branches is very 

 .similar to that found in Chlorops. There are many differences of 

 detail which do not, however, merit the extended description 

 necessary to make them clear: one difference <»nly is noteworthy. 

 In Chlorops the (lorsal commissures give off no branches to the 

 dorsal region of the body, whicTi is supplied by bi-anches from the 

 lateral trunks. In Meromyza (text-fig. 10(3) each dorsal com- 

 missuie, except the second and the last, gives off two anteriorly- 

 <lirected branches, which i-amify extensively to supply the dorsal 



