417 



and reproducing on clovers, and Phorodon humuli, alternating between 

 plum and hop, and chiefly injurious to the latter. 



Another group contains species of which the summer hosts alone 

 are of economic importance, such as Macrosvplmm solanifoUi, Ashm. 

 (potato aphis), infesting tomato, potato, egg-plant, cotton and lettuce, 

 and M. granarium, Kirby (grain aphis), infesting grains and grasses, 

 species that in the north migrate in autumn to roses, but in the south 

 remain on their summer hosts. In California they feed and reproduce 

 in the winter both on roses and on their smnmer hosts. Other members 

 of this group are : — A. cerasifoliae, Fitch (possibly a synonym of 

 A. padi, L.), on grains and gi-asses and hibernating on choke-cherry ; 

 A. rumicis, attacking many varieties of beans and wintering on Eiiony- 

 mus in temperate climates ; Rhopalosiphum capreae, Kalt. (parsley 

 aphis), sometimes a pest on umbelliferous crops, and wintering on 

 willows ; Macrosiphum illinoisense, Shimer (eastern grape aphis) 

 migrating in the autumn to, and ovipositing upon, Viburmim opulus ; 

 Pemphigus betae, Doane (beet aphis) ; and Eriosoma lanigerum, Haus., 

 and E. ptjricola, B. & D. 



A third group contains those species whose winter hosts alone are 

 economic plants, such as : — Rhopalosiphum lactucae, Kalt., which 

 migrates between currant, gooseberry and sow-thistle (Sonchus) ; 

 Myzus ribis, L,, wintering on currants and migrating to and from 

 Stachys and Leonurus (Menthaceae) ; Aphis malifoline, Fitch (rosy 

 apple aphis), migrating between apples and rib-grass and plantains ; 

 Aphis setariae, Thomas (rusty plum aphis), passing the summer on 

 grasses ; Hyalopterus arundinis, F. (mealy plum aphis), Rhopalo- 

 siphum nymphaeae, L. (reddish-brown plum aphis), and Aphis cardui, 

 L. (green plum aphis), passing the summer respectively on reeds, 

 water-plants and thistles. 



Of the above twenty-one species, at least fourteen, and possibly 

 fifteen or sixteen, are common to Europe and America, while strictly 

 European economic species with alternate host-habits have not been 

 dealt with. 



QuAYLE (H. J.). Cyanide Fumigation : Diffusion of Gas under Tent 

 and Shape of Tree in Relation to Dosage. — Jl. Econ. Etit.om., 

 Concord, N.H., xi, no. 3, June 1918, pp. 294-299, 1 fig., 1 plate. 



Owing to the variable results obtained in practice, it was found 

 necessary to determine experimentally the relation between the dosage 

 and the shape of the tree, since the latter varies between such wide 

 limits, as that of the low and broad lemon tree — the circumference of 

 which is twice the distance over the top — to that of the orange seedling, 

 where the circumference and the distance over the top are equal. 

 At the same time it was required to discover the killing power at 

 different levels within the tent, which was effected by placing insects 

 one foot from the top, one foot from the bottom, and at the centre. 



In these experiments frameworks measuring 31 feet by 31 feet and 

 22 feet by 44 feet were covered with octagonal fumigation tents, 

 both tents being charged at the same time. 



The results showed little difference in the killing efficiency of the 

 gas at the top and centre of the tall tree, but a great difference between 

 that obtaining in these positions and at the bottom of the tree, probably 



(C496) X 



