I 9 II.] 



Aphides, or Plant Lice. 



827 



Life-History. — Fertilised eggs are laid in the autumn on the 

 twigs and at the base of the buds. The winter is passed in the 

 egg stage. Hatching takes place in spring, the young from 

 the eggs developing into adult females, which are wingless 

 and give rise to live young. These in turn become adult 

 wingless viviparous females. As the season advances some 

 of the young, instead of developing as stated, show wing- 

 rudiments and develop into winged viviparous females. These 

 may spread the infection. Late in the year males and wingless 

 egg-laying females are found, and fertilised eggs are laid, 

 which remain unhatched over the winter. 



Treatment. — (1) Spraying should take place with soft-soap 

 and quassia wash, or with paraffin emulsion, early in the 

 year, when the young Aphides are noticed to have hatched out. 

 The spray should always be applied before the leaves have 

 curled. (2) Spraying should also be done in the autumn with 

 paraffin emulsion, in order to kill the egg-laying females, e.g., 

 late in September or during October. (3) Theobald writes 

 favourably of a late winter wash, where the pest is abundant, 

 the plums and damsons to be heavily sprayed with lime-wash, 

 salt, and water-glass just before the bursting of the buds. This 

 wash is said to prevent the hatching of eggs ; the formula given 

 is 1 cwt. lime, 30 lb. salt, and 5 lb. water-glass to 100 gallons 

 of water. 



Another Aphid found on plums and allied fruit plants is 

 Hy alopter us pruni, Fab. As a spray against this Aphid, 

 which is found on the under surface of the leaves, Theobald 

 quotes a correspondent's treatment as very satisfactory, viz., 

 paraffin emulsion, with 1 lb. of liver of sulphur added for every 

 100 gallons of the wash. 



A third Aphid which in certain stages of its life-history is 

 found on the genus Primus is Phorodon humuli, described in 

 Leaflet 88. This species is distinguished from the others by 

 two marked projections from the forehead, between the 

 antennas. 



3 M 2 



