130 PREDACIOUS AND PARASITIC 



tubes are encased in tissue similar to that enveloping the sperma- 

 thecse themselves, and their inner coat is continuous with that of 

 the interior of the capsules. The latter are lined with epitheHal 

 cells of an angular form and of a dark brown colour, which may 

 readily be seen on breaking the capsule by a little pressure on the 

 cover-glass, when also the junctions of the edges of the capsules 

 will often be evident. The three spermathecae are in some species 

 grouped together in a surrounding membranous network ; but in 

 some, as Syrphus luniger, they are arranged two on one side and 

 one on the other, as in the Blow-Fly. 



The Classification of the Syrphid^. 



It has already been mentioned that this family has been divided 

 by entomologists into something like forty genera, which are 

 inhabitants of Britain. But this has not been accomplished 

 without vast labour and an immense number of changes in the 

 arrangement. Over and over again, by Fabricius, Meignen, 

 Walker, Fallen, and others, genera have been constituted, recon- 

 stituted, and abandoned, and, not uncommonly, so complete has 

 been the change that the generic names seem to have been trans- 

 ferred from one group of species to another. 



I do not propose to enter upon an examination of the whole 

 of this extensive family. Such a course would be beyond the 

 scope of the present work, but it may be useful to students of the 

 Aphididae if I quote from the admirable List of British Diptera, 

 arranged by Mr. G. H. Verrall, the particulars of those genera in 

 which aphidivorous larvae are most likely to occur. 



The earliest writer to attempt any division of the family was 

 Harris, who, writing a few years after Scopoli had separated the 

 Syrphidce from the Linnaean genus, Musca, constituted three chief 

 divisions based upon the distinctive wing-neuration, as shown in 

 Vol. IV. on PI, XVI., Figs. lo, ii, and 12. Although this divi- 

 sion has not been adopted by later writers, it is convenient for the 

 purpose of dividing the family into sections, and I have found it 

 useful to group it under the heads Syrphidince (Fig. 12), Eristalince 

 (Fig. 11), and VolucellidcB (Fig. 10). 



Donovan gave some illustrations of this family at the end of 

 the last century, and between 1825 and 1840 J. Curtis published 



