210 



DIPTERA OR TRUE FLIES. 



with paraffin-oil and soap, rubbed with a sponge. Miss Ormerod 

 mentions soluble phrenyl as useful in one of her reports. 



The rest of the flies belong to the section Cyclorrhapha, which 

 is divided again into the Proboscidea and Sprobosctdea. The 

 Proboscidea contain the majority of flies, the following being 

 the most important economic forms : — 



Hover-flies, or Syrphidae. 



The Syrphidfe are all moderate-sized flies, often brilliantly 

 coloured, generally with banded bodies, yellow and black or 

 brown being the predominating colours. They hover in the air 

 like a hawk, suddenly darting off and again remaining quivering 



Fig. 103. —Hover-flies (Syrphidce). 



1, Sifrplius halteatus; 2, larva devouring aphis; 3, pupa; 4, GataboTiiba pyrastri ; 5, 

 larva ; 6, pupa ; 7. Syrphus ribesii. (Curbis.) 



at a fresh spot. We only see them in the bright sun, and may 

 notice them flying and hovering over plants, upon the nectar of 

 which the adults feed. At other times we see them busy over 

 colonies of Aphides, for here they deposit their eggs, their 

 curious, almost repulsive-looking larvae (fig. 103, 2 and 5) feeding 

 upon plant-lice, which they devour with great rapidity. The 

 larvae are yellow, green, or red in colour, with a narrow anterior 



