HOW TO COLLECT DIPTERA (tWO-WINGED FLIES) . 65 



To support the discs No. 16 should be used ; but, if these cannot 

 be obtained, common pins may be employed. 



Gun-wad punches, Nos. 4, 12, and 20 bores (from any gun-maker), 

 for punching discs of card. 



Cards (3- or 4-sheet Bristol board), from which to punch discs ; a 

 supply of the latter should be prepared ready for use. 



A pla.tyscopic lens (Messrs. Baker, 244, High Holborn, London, 

 W.C. ; or John Browning, 63, Strand, London, W.C. : price about 

 15s.). The magnifying-power should not be too high — from 10 to 

 15 diameters is about the best. 



Cork-carpet or pith. — Two or three sheets about 6 inches square, 

 on which to perform the operations of pinning, etc. (Cork-carpet 

 can be obtained at Harrod's Stores, Brompton Boad, London, 

 S.W.) 



Two or three cork-lined entomological store-boxes. — These can be 

 obtained from Messrs. Watkins k Doncaster, 36, Strand, London, 

 W.C, or any other dealer in natural-history apparatus. For a 

 collecting trip or expedition of some duration the boxes should not 

 be smaller than about 18 inches by 12, and they must be sufficiently 

 deep to prevent the heads of the pins from coming into contact 

 when both sides of the box are filled. Should the collector run 

 out of store-boxes, cigar-hoxes, in the bottom of which is fixed a 

 layer of cork-carpet or pith, make efficient substitutes ; but if 

 pith is used, it should not be less than | inch thick. 



^ How TO DISTINGUISH DiPTERA FROM OTHER TnSECTS. 



Disregarding a few abnormal wingless forms, Diptera may be 

 distinguished from all other insects by the fact that they possess 

 only one pair of wings, and are without caudal filaments. Thus, 

 besides ordinary flies, such as Blue-bottles and House-flies {Muscidca), 

 the Order also includes Midges {Chiro7iomidce), Gnats or Mosquitoes 

 (Culicidce), Daddy-long-legs [Tipulidw), HorFe-flies {Tahanidoi), etc. 



How TO DISTINGUISH THE SeXES. 



In the majority of Diptera the sexes may easily be distinguished 

 by the fact that the eyes meet together (or nearly so) on the foie- 



