BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [56] 



require the most delicate treatment, and the greatest care must be 

 exercised both in collecting and handling. A light sweep net is the 



best implement for collecting and the 

 contents of the net should frequently 

 be emptied into bottles provided with 

 blotting paper to absorb the excess of 

 moisture. Very small Diptera should 

 not be killed when 

 they can not be imme- 

 diately pinned, and 

 hairy flies should 

 never be taken from 

 the net with the hand, 

 but should be handled 

 with fine forceps. A 

 pair of special collecting shears has been used by 

 Lord Walsingham very successfully. It is repre- 

 sented in the accompanying figure, and consists of 

 a pair of screen-covered disks, between which the fly 

 is caught. The insect is at once i)inned through the 

 screen and may be removed and transferred to a 

 box containing a sponge soaked in chloroform. The 

 use of this implement is especially advisable in the case of the Bee-flies 

 (BomMliidce) and other hairy forms which are liable to be rubbed when 



Fig. 78.— Ox Bot-fly (Hypoderma bovis) 

 enlarged. (After Brauer.) 



% ^ 



Fig. 79.— The Collecting 

 Shears. ( After Kiesen- 



wetter.) 



Fig. 80.— A Bee-fly (Antftraa; hyimmelas) . a, larva from side; 6, pupal skin protruding from cutworm 

 chrysalis; c, pupa; d, imago — all enlarged). 



collected in the ordinary net. The Gall-making Diptera f CecidomyidceJ 

 are of little value unless accompanied with their galls, and the aim 

 should always be to collect the galls and rear the insects rather than 

 the keeping of specimens taken in the course of general collecting with 

 a sweep net. The rearing of Cecidomyidfe is, however, a dehcate task, 

 and requires considerable experience. Some knowledge of the habits 



