122 PREDACIOUS AND PARASITIC 



instances a slightly marked black line along the dorsum. The fly 

 which emerges is invariably Syrphus luniger, and is figured on 

 PL XVI. of Vol. IV., together with the larva and pupa. 



A larva occasionally met with, and more especially in fruit and 

 kitchen gardens, is, I think, smooth, save for the creases of the 

 skin, plump, and of the colour of parchment. It is frequently 

 marked with blotches, which are generally situate on either side of 

 the medial line of the dorsum, and which vary in colour from dull 

 yellow to dark brown and black. These patches are due to masses 

 of pigment underneath the skin, through which they are visible. 

 The pupa-case is similarly parchment-like in appearance, free from 

 speckling, and sometimes slightly ribbed, especially after the 

 escape of the fly, which belongs to the same genus as the last des- 

 cribed, though to a different species. It is Sy7'phus topiarius. 



The third variety which I have succeeded in identifying is a 

 smooth skinned grub, far from common, of a pale green colour, 

 and having a more or less marked stripe of pink or carmine down 

 the centre of the back. This larva eventually produces the fly, 

 Caiabomba pyrastri. 



Besides these, I have made repeated attempts to rear an aphi- 

 divorous larva, small, greenish, or grey in colour, nearly or quite 

 smooth, with very delicate markings, and generally having fine 

 lines of light carmine on the dorsum and around the lateral edges. 

 These larvae habitually undergo long fasts and periods of inactivity, 

 and the specimens which I have succeeded in keeping alive for 

 several months have in each instance succumbed to the attacks of 

 a fungoid growth, which seems to affect the mouth parts. But I 

 have also reason to think that the larva of Flatychirus albimanus 

 is aphidivorous in its habit, and if so, it would seem to me to be 

 exceedingly probable that the larva last described belongs to that 

 species. 



It is impossible to say, from only a few seasons' experience of 

 the counties of Somerset and Gloucester, whether all the aphidi- 

 vorous varieties have been observed. One, S. balteatus, is known 

 to be an aphis eater, and I have on one or two occasions reared it 

 from larvae closely resembling those of 6". luniger^ but have failed 

 to identify the grub from the others. The larva of S. ribesii is 

 also no doubt aphidivorous. 



