826 



Aphides, or Plant Lice. 



[JAN;, 



The egg-laying female is green, with rows of dark spots on 

 the back ; the eggs are green at first, but later are black. 



Life-History. — Young Aphides hatch from eggs laid in the 

 previous autumn on cruciferous plants (both wild and culti- 

 vated). During the summer the wingless and winged virgin 

 females are found. The winged females spread the infec- 

 tion. Both the wingless and the winged females produce 

 live young. Towards the end of the season, when infestation 

 is worst, males and wingless egg-laying females pair, and 

 fertilised eggs are laid from which in the next year come the 

 individuals which start the colonies for the year. 



Treatment. — (i) Cruciferous weeds should be kept down as 

 far as possible. (2) The insects should be attacked early with 

 soap and water, and the watering should be repeated. 



On large areas, as in field cultivation, no treatment will 

 avail when widespread attack has been neglected. 



Rose Aphides. — Different species of the genus Siphono- 

 phora are found on roses. One of these, S. rosce, migrates to 

 teasel and returns later in the year. 



Treatment. — Spraying should be done with the soft-soap 

 and quassia spray, but only 41b. of soap should be used. 

 Spraying should be carried out twice in the same week. 



The Plum Aphis (Aphis p-runi, Reaumur). — This Aphis is 

 a serious pest on plum, damson, and allied Rosaceous fruit 

 trees. The loss of sap due to its feeding causes the leaves to 

 curl and discolour, and the young fruits fall off. 



The eggs found in autumn and winter are shining black. 

 The young from the eggs are green or dark green ; they de^- 

 velop into wingless viviparous females, which vary in colour 

 from green to olive-brown. The pupal stage or stage preced- 

 ing the winged viviparous female is characterised by rudi- 

 ments of wings or wing-cases ; the body is green and the wing- 

 parts brownish. The winged viviparous female is apple- 

 green, with the antennae, head, upper surface of thorax, and 

 the feet, black. 



Of the sexual individuals, the males are small ; they have 

 wings and are yellow-brown or black in colour ; the egg-laying 

 females are small and wingless; they are greenish-yellow in 

 colour, and transparent. 



