— 119 — 



SOME STUDIES OF THE FECUNDITY OF THE 

 APPLE-LEAF PLANT-LOUSE. 



Aphis iiiali Kilch. 

 By F. ^\. \Vi.i!STKk. 



Of the tliree principal species of Apliides infesliii!^- our smaller 

 cereal «;rains, this species occupies an anomalous and at the same 

 time important position. In point of numbers it is usually in 

 advance of Toxoptcra i::;raiiii/ii//ii, antl, usually, of Siplioiiophora iwcme^ 

 and its effects on young wheat duriuii' the fall is, if anythinj^ more 

 serious than either of the others, especially if the land be poor 

 and the weather be dry. So far as my own observations go, it is 

 more detrimental to the wheat than to the apple. 'l"he occurrence 

 of the eggs on the twigs of apple, during winter, and the appear- 

 ance of the young on the first tender buds and leaves in the 

 spring, ;ire familiar to all horticulturists. I have several times 

 made the attempt to colonize the species on wheat plants, with 

 individuals taken from the apple, but was never able to thoroughly 

 succeeil in this until this year, when a series of experiments was 

 begun in the insectary which swept away any i)rcvious doubts on 

 the subject of migrations. 



Several years ago, on April 17th, all stages of y^ w^?// were 

 found on the young buds of cpiince — a new food plant so far as 

 published record goes — and being unrecognizable without the 

 winged adults, the attempt was made to carry them on artificially 

 until these would appear. In doing this a number escaped from 

 the breeding cage where they were kept, and took up their abode 

 on some young wheat, growing in a box on the same table. Not 

 knowing with what generation I l)egan investigating it on the 

 ([uince, it is of course impossible to say whether, as with the Hop 

 Aphis, it is not until the third brood is reacheil that adults attempt 

 to escape to other plants, and if it was to this third brot)d to which 

 the escaped individuals belonged. It will be only safe to say that 

 they were wingetl and migrated. A wingless female from the 

 tiuince also strayed from the cage and stationed herself on some 

 of these wheat plants, and produced a number of young, but these 

 all died and fell from the plants. At the same time, in a large 

 cage out of doors, others of this species were being reared from 

 the eggs on twigs of apple. Wheat was sown within this cage, 

 and some of the winged adults, after leaving the young buds and 



