41 THE EEPOET OF THE No. 36 



may have arisen. In the fall, apterous ovipars and apterous males -put in an ap- 

 pearance. The sexes mate and the females deposit their eggs on twigs and water 

 si^routs. 



The Rosy Apple Aphis {Aphis malifolioi Fitch). Like many another 

 rogue, this insect has heen living amongst us under a false name. In a recent 

 letter, Mr. A. C. Baker, of the IT. S. Bureau of Entomology, informs me that its 

 correct appellation is Aphis molifolice Fitch, and not A. sorhi, nor yet the more 

 recent A. I'ochii. It appears that Kaltenbacli's A. sorhi from Sorbus and Schoute- 

 den's I'ocliii (pyri Koch) from apple are quite distinct from our rosy aphis. 



This species is often very destructive in apple orchards. It has a marked 

 preference for, and confines its work largely to the lower, inner and shady portions 

 of the trees. It not only curls and destroys foliage, but by feeding on the leaves 

 "adjacent to fruit clusters, and on the fruit itself, it produces bunches of deformed, 

 dwarfed and unmarketable apples. The rosy aphis is essentially a pest of the 

 bearing orchard. So far as our observations have gone, it seldom occurs on, and 

 is never injurious to nursery stock. This partial immunity is largely due, I think, 

 to the fact that young trees do not afford the aphis — a shade loving insect — suit- 

 •able shady quarters. 



The eggs of this species hatch about the same time as those of Aphis pomi. 

 The stem-mothers become mature in twenty days or so, and begin to give birth to 

 young at an alarming rate. According to our 1915 experiments each female may 

 produce from 67 to 260 5'^oung (data obtained from 12 individuals). The second 

 generation resemble their mothers to a great extent in rate of development, in 

 fecundity and in the absence of wings. During a period extending from mid- 

 June to the latter part of July, the thii'd generation lice acquire wings and migrate 

 to and establish colonies on Plantago lanceolaia, and P. major, chiefly the former. 

 (It should be mentioned here that a small percentage of the migrants may belong 

 to the second and fourth generations). On the secondary food plants, the aphides 

 breed rapidly, and as many as eleven broods may arise. In the autumn alate 

 sexuparse andl alate males appear and fly back to the apple. The sexuparae give 

 birth to young, which in three or four weeks' time became mature- apterous 

 oviparse. After being fertilized by the males the oviparffi lay their eggs on twigs 

 and branches — in crevices and around the base of buds. 



The Oat Api-iis {Aphis avence Fabricius). In the spring, this aphid, as a 

 general rule, is much more abundant than the two preceding species, but as it 

 only remains on the apple for a comparatively short time, it is not so injurious 

 as they are. It attacks the foliage, the blossom stems, and sometimes the petals. 



The eggs of the oat aphis commence to hatch several days before those of 

 Aphis pomi and Aphis malifolicp.. The stem-mothers develop rapidly, and most 

 of them are mature and are reproducing by the time the apple blossoms are show- 

 ing jDink. In the matter of reproductive capacity, they are very much like the 

 stem-mothers of A. pomi — each female may give birth on an average to 76 young 

 (average obtained from 9 individuals, 1915 experiments). The majority of the 

 second and the whole of the third generation become alate, and during a period 

 extending from mid-May to mid-June, migrate to their summer food plants — 

 various grains and grasses. On these hosts, the aphides feed and breed until 

 fall, at which time the return migration to apple takes place. As in the case of 

 malifolice, the males are produced on the secondary, and the sexual females on 

 the primary host. 



The Woolly Aphis of the Apple {Eriosoma lanigera Hausmann). This 

 cosmopolitan bark-feeding aphid is ^ very destructive apple pest in certain countries. 



