29 



The Turnip Aphis. (Aphis brassicce.) 



(PLATE V.) 



Injury to a considerable extent was caused to turnip and 

 swede plants during last summer by the turnip aphis. Cabbages 

 of all kinds were also attacked in some places. Several speci- 

 mens of infested plants of turnips and cabbages were sent for 

 the identification of their affection. Cattle cabbages suffered 

 somewhat seriously from these aphides, which penetrated even 

 to their innermost leaves ; and cauliflowers also were damaged, 

 and their appearance spoilt for market. 



The aphides congregate on the under surface of the leaves of 

 swedes and turnips, where they increase with wonderful rapidity, 

 and suck up the juices of the plants with their beaks, or rostra. 

 Added to which, their filth and " honey dew " fall on the lower 

 leaves, stopping up their stomata, and hindering respiration. 

 After a short time the larvaa change colour. The growth of the 

 roots is stayed, the stalks, or shanks, of the plants are elongated 

 unnaturally, and finally the crop is ruined, or the weight of 

 roots is materially lessened, and the leafage made untit for food. 



As a rule, these aphides are not seen on turnips and cabbages 

 very early in the season as other aphides, those of the hop, 

 lime, rose, for example. At least, they have not been noticed 

 until the plants have attained a fair size. The first 

 generations are bred on cruciferous weeds, as charlock, wild mus- 

 tard, penny cress and others ; and winged viviparous females fly 

 from these, or are borne by the wind, to cultivated plants. 

 Mr. Buckton says : " This species feeds on a variety of plants, 

 such as Rapharviis salivus, Capsella bursa pastoris, Sinapis 

 arvensis, jind the garden cabbage, Brassica oleracea, both 

 the upper and under sides of the foliage of which last plant 

 it often crowds with such numbers that the leaves become 

 hidden by the living mass. Indeed, sometimes, weight for 

 weight, there is more animal than vegetable substance present. 

 The leaves then become putrid, offensive in odour, and quite 

 disgusting to the eye."* 



DESCRIPTION AND LIFE HISTORY. 



The winged viviparous female (Plate V. c) has a black head and 

 thorax, with a green or yellowish-green abdomen, and very dark 

 yellow legs. The antennae are brown ; the legs dark brown. The 

 cornicles are also brown. The wings are rather short, with dark 

 stigmata. Upon settling down on plants whose food supply is 



* A Monograph of British Aphides, by G. Bowdler Buckton, F.R.S., vol. 2, 

 p. 34. 



