DIPTEROUS TRIBE OF SPH^ROCERID/E. SS5 



Sp. I. H. pusilla. 



Copromyza pusilla . Fallen, Heterom. 8. No. 5. 

 Borborus pusilla . . Meig. VI. 206. No. 22. 

 Heteroptera pusilla . Macq. S. a B. II. 570. No. 1 . 



Resembles a Limosina : the principal cross nerve is placed so slant- 

 ing that it becomes confounded with the 4th main nerve, but 

 forms with the 5th a very acute angle advanced towards the 

 margin of the wing : the 2d nerve is also continued nearer to the 

 tip : black : thorax and scutel pubescent ; the latter shorter than 

 the metathorax : legs finely pubescent ; not many bristles on the 

 middle shanks ; first joint both of the fore and hind feet acutely 

 produced at the tip, in the latter triangular : poisers whitish : 

 wings whitish hyaline, or dusky ; nerves blackish brown. 

 (Length 1 ; wings 2 lines.) 



Taken by Mr. Walker, near London ; and in the Isle of 

 Wight. 



The larva of Borborus equinus is like that of Scatophaga 

 stercoraria in general form. The skin is quite transparent, so 

 that the internal structure and the minutest ramifications of 

 the tracheae can be seen through it ; but I could not dis- 

 cover any trace of arterial circulation. The pulsations of the 

 dorsal vessel were from 90 to 110 a minute. The skin is 

 closely set with very minute erect points or short bristles, most 

 thickly on the last segment. The mandibles come out under 

 two conic processes of the head, each of which bears a smaller 

 appendage of similar form on the upper side. The anterior 

 opening of the tracheae is furnished with the usual fan-like 

 process. The intermediate segments have no inequalities of 

 any kind. The last has the usual conic protuberances behind 

 the anal cleft, and its margin bears a circle of smaller ones ; 

 those being the least which lie immediately above and below 

 the openings of the tracheae, which are of the usual form, each 

 consisting of three oblong spiracles surrounded by a dark ring. 

 The full grown larvae, when extended, are about 4J lines in 

 length. They do not enter the ground to undergo their 

 transformation. Of a number out of eggs laid the first week 

 of October, but few had changed at the end of that month ; 

 but probably the period is less in summer, as Meigen says that 



