The Syrphus Flies 



The habits of the syrphus flies in their early stages vary 

 greatly. Very many of them in the larval state feed upon plant 

 lice and other small, soft-bodied insects. I have seen currant 

 bushes upon which there was hardly a leaf which did not support 

 a thriving colony of plant lice and which had not become curled 

 and distorted in consequence, and yet within a very few days, 

 while the distortion of the leaves remained, not a plant louse was 

 to be found but under each leaf instead of the flourishing group 

 of lice was a fat, full-grown syrphus larva which had destroyed 

 all of the previous inhabitants and was now ready to transform. 



These larvae do not have a distinctly differentiated head. 

 The external mouth-parts are either entirely lacking or there are 

 two or four usually dark-colored booklets. The body is smooth 

 and usually glistening. When ready 

 to transform, the last skin of the 

 larva contracts and hardens and 

 assumes an oval shape and a darker 

 color and the pupa is formed within 

 it. When the fly is ready to emerge, 

 the front end of the old skin is 

 pushed out and the perfect fly 

 escapes. The booklets on the 



mouth of the larva occur with those ^'S- S3--MaUota posticata and 

 , n 1 1 • I ^ J puparium of same. 



syrphus fly larvae which feed upon *^ 



other insects and they serve to grasp and pierce the body of the 

 prey. Those larvae which do not have such booklets have other 

 habits. They may feed in the decaying wood of old trees or 

 logs; they may live in manure or soft mud impregnated with de- 

 caying vegetable matter; they may be found in the sap of trees 

 or in the stems of certain tender plants or in fungi. Still others 

 are common in ants' nests and others again are guests in the 

 nests of bumblebees. With such variable habits there must 

 necessarily be considerable variation in structure and as a result 

 of this mode of life those forms which live in soft mud or manure, 

 which may be almost a liquid, and some of those which live in 

 very damp, decaying wood, have long slender projections at the 

 end of the body bearing spiracles or breathing holes at the tip, so 

 that when the body of the larva is buried in the semi-liquid mass 

 in which it is feeding this long tail still protrudes to the air, 

 enabling it to breathe in comfort. These larvae have been termed 



151 



