12 H. C. EFFLATOVN. 



longitudinal lines. It very often bears a distinct soft pubescence 

 which may either be very slight and inconspicuous, or quite long, 

 close and dense, but which hardly ever bears any bristles or bristly 

 hairs. Scuttellum usually resembling the thorax in colour and 

 pubescence and sometimes bearing bristly hairs on its margin which 

 provide important specific characters. 



Abdomen varying very much in shape and colour and com- 

 posed of five or six visible segments and never bearing any bristly 

 hairs. Hypopygium nearly always asymmetrical and usually not 

 prominent; the abdomen is generally thinly pilose or bare, but some- 

 times clothed with dense pile or dust or both. 



Legs usually moderately strong, but varying very much in 

 shape and pubescence and when bristles are present they are found 

 only on the under surface of the femora. The females of all species 

 have the legs reduced to a very simple form. Sometimes the tibiae 

 and the apices of the tarsal joints bear small apical spurs and occa- 

 sionally the hind trochanters and femora are armed beneath, 

 especially in the male, and these afford valuable characters for 

 distinguishing species. 



Wings comparatively large and with a specialised and distinct- 

 ive venation. Radius 4 + 5 never forked; Media 1 + 2 terminates 

 in Radius 4 + 5 well before or near the tip; Cell Rl either opened 

 or closed; basal cells large and well distinguished; cell Al elongated 

 and always closed before the border of the wing. Running right 

 across the radio-median cross-vein, between Radius 4 + 5 and Media 

 1 and almost parallel with them, the vena spuria or false vein is 

 nearly always present. Although this false vein is characteristic 

 of the family so that its presenoe certainly secures the admission 

 or any species to this family, its absence does not exclude a 

 species, as it often exists in a very faint or almost imperceptible 

 form. Alulae always distinct and nearly always well developed. 

 Squamulae small or fairly large with a distinctly thickened 

 margin and almost always with delicate fringes which may be 

 composed of simple or compound hairs. Halteres usually moderate 

 in size. 



The Syrphidae form one of the largest, most sharply defined, 

 and best known of all the families of Diptera. There are over 

 2500 species known throughout the world. They occur in all 

 regions from the Tropics to the Poles. They contain among them 

 many of the brightest coloured flies and in the sunlight are 

 remarkably good hoverers and usually very active fliers. The adults 

 are almost always attracted by flowers, especially Composites, 

 UmbeUiferae and Rosaceae. Some species fly in and out about low 

 herbage and flowers and others may be seen resting on leaves and 



