382 



Evidently from this list Kaltenbach had confused several 

 species, owing to their similarity in colour and form. 



ScHOUTEDEN {Cat. Aphid. Belg., p. 240) gives as food plants 

 for M. ulniariœ Schrank the following : Colutea arborcscens, 

 Genista tinctoria, Robinia pscudacacia, Trifolium var. sp., 

 Spirœa ulmaria, etc. 



Ferrari {Aphid. Liguriœ, p. 54) gives as food plants " Geo 

 urbano, Rosis cultis, et Hyosieride radiata." 



Buckton {Mono. Brit. Aphid., i., p. 135), besides saying it 

 affects a large number of plants besides the pea, also says 

 " The glaucous female in PI. XIV was taken on the common 

 nettle Urtica dioica." 



The specimen figured is evidently not Kaltenbach's pisi 

 at all. Davidson {Journ. Eco. Ent., iii., p. 380) also mentions 

 it as occurring on Urtica hol sérica. 



From a careful examination of the Green Aphides of the 

 Genus Macrosiphum (formerly called Siphonophora) found on 

 the Meadow Sweet {Spirœ a ulmaria), the Avens {Geum urbanum), 

 the Peas {Pisum spp.). Bird's Foot Trefoil {Lotus corniculatus) , 

 and Stitchwort {Stellaria graminea), I find they are all distinct 

 and well-marked species. The Green Aphis on the Rest Harrow 

 {Ononis arvensis), the Siphonophora ononis Koch, is also evi- 

 dently' quite distinct, judging from a single alate specimen I have. 



All these Aphides bear a very strong resemblance to one 

 another, so much so that one can quite imagine Kaltenbach 

 and others grouping them together. 



When, however, one examines the structure and ornamenta- 

 tion of the antennae and cornicles, marked differences can be 

 seen between certain of them. 



In the alate females these characters are most marked; the 

 number and disposition of the sensoria of the antenme and the 

 sculpturing of the cornicles are easily demonstrated in specimens 

 mounted in Canada balsam, and this also applies to the apterous 

 females, but not quite to the same extent. In the nympha; 

 these characters are frequently absent, however. 



We can divide this group of Macrosiphum primarily into 

 two : 



A, the pisi group, in which the cornicles are entirely imbri- 

 cated, and sensoria occur on the third antennal segment. These 



