30 



grateful to them, these females produce larvae, or " lice," which, after 

 the manner of aphides, bring forth many generations like themselves. 



These wingless viviparous females (Plate V. a and 1} have oval 

 bodies, and are covered with a whitish, powdery substance after 

 they are a few days old, which hides their natural green colour. 

 When first born they are yellow, shining, and have no powdery 

 material upon them. In course of time egg-laying females are 

 evolved. It is not known where the eggs are placed, but pro- 

 bably upon cruciferous weeds in hedgerows, clover leys, and 

 other places. And, as in the case of other species of aphis, at 

 the end of the season, or when the supplies of food fail, or 

 become unsuitable, winged egg-laying females are generated 

 which fly, or are wafted through the air, to plants suitable for their 

 purpose. 



It is certain that continuity of existence is not preserved 

 upon the turnip and cabbage crops, except perhaps upon autumn 

 planted cabbages, as they are consumed or carried away, and 

 the ground is ploughed up at once to be sown with corn. There- 

 fore, it must be assumed that the eggs are put by migratory 

 females upon wild cruciferous plants. And, without doubt, 

 some of the wingless viviparous females may be left upon wild 

 cruciferge, and hibernate at their roots. No amount of cold 

 appears to affect them, as they have been seen upon plants and 

 producing young in February after the coldest weather. 



METHODS OF PREVENTION AND REMEDIES. 



It has been proved, without the least doubt, that solutions of 

 quassia and soft soap, if applied in due time and properly, soon 

 clear away hop aphides, whose habits resemble those of the 

 turnip aphides. The soft soap causes the bitter principle of the 

 quassia to stick to the leaves and make them unpalatable ; while 

 the aphides themselves are most unpleasantly affected by the 

 wash which adheres to them. 



From 7 to 8 Ibs. of soft soap and the extract of from 8 to 9 Ibs. 

 of quassia chips are the best proportions for 100 gallons of water, 

 and are those of which " hop wash " is ordinarily composed. 



For this aphis two or three, or eVen four, quarts of carbolic 

 acid, or paraffin oil, may be used, instead of quassia, upon swedes 

 and turnips. 



These washes may be put on with large garden engines having 

 strong pumps and two lengths of indiarubber hose, with spray 

 jets somewhat curved that they may be got under the leaves, 

 for distribution. Hop-washing engines, which are stronger, 

 would also be useful for washing turnips and cabbages. Both 

 these and the garden engines must be set on high wheels in order 

 to go over the rows of plants. Narrow, long-bodied engines 

 might be constructed to go between the drills. 



The wash may also be put on by the Strawsonizer, as adapted 

 to throw the liquid up under the turnip leaves. On small 



