512 



Plum Aphis. 



abdomen, olive brown antennae, and brown cornicles ; the whole 

 body above and below is covered with a mealy down. These 

 apterous females soon commence to produce living young, which 

 rapidly mature and produce other young. This asexual repro- 

 production of wingless forms goes on for some time, and under 

 favourable conditions to such an extent that the leaves, which 

 have gradually curled up, die off. As food supply commences 

 to fail these lice, instead of turning to wingless viviparous 

 females, enter a pupal stage, rudiments of wings — " wing-buds " 

 — appearing. The pupa is shining green and dull yellowish, 

 the wing-cases tipped with dark brown ; the green cornicles 

 also tipped with black. The pupal form has been observed in 

 the first week in June, and again in July. Sometimes all the 

 lice on a tree enter this stage at once, at other times only 

 a few. 



The winged female coming from the pupa is also viviparous — 

 in colour she is apple green, with black head, thorax, and 

 antennae ; on the green abdomen is a dark patch and dark 

 lateral spots ; the wings are irridescent with brown veins. 

 These winged viviparous females fly about and settle upon 

 other trees, thus setting up fresh colonies. Their living young 

 grow into apterous viviparous females, which carry on rapid 

 reproduction like the first series. 



In the autumn the pupal stage is assumed again, but from the 

 pupae now come winged males and wingless oviparous females. 



The winged male is small, with a dusky ochreous body and a 

 dark brown head, markings on the thorax, and three on the 

 abdomen. The colour varies considerably, some males being 

 almost black and some wholly black, according to Buckton. 



The apterous oviparous female is pale yellowish-green, almost 

 transparent, with brown cornicles. This female, after being 

 fertilised by the male, deposits little shiny black- eggs at the 

 base of the buds and on the twigs. Egg-laying may commence 

 early in October, and goes on until November. These eggs 

 usually hatch early in April, but the lice have been observed as 

 early as March. Not only are the. eggs laid on prunes, but also 

 on the apple, and probably on peach and nectarine. They are 

 firmly attached by a gummy excretion by the parent, and are 

 too thick-shelled to be affected by caustic alkali wash. 



