1*. II. AwATi 259 



the nymphs to the time when they laid eggs. The results of those 

 different catches are given below: — 



363 372 



It seems clear that there is no great disproportion in the sexes and 

 no reason to anticipate parthenogenesis. 



Habits of the Adults. 



(a) Change of colour. The adults, both male and female, undergo 

 some change in colour as they grow older. The uniform brown, pale 

 green, or deep green gives place to a tinted pattern of the same. Some 

 females of reddish brown have been found. 



(6) Feeding habits. The males and females sit on the leaves — either 

 on the upper or lower surface. They are very harmless in this stage, 

 though they produce certain characteristic symptoms of their presence. 

 They suck the juices of those leaves, which become marked with very 

 minute circular white spots. These spots seem to increase in size and 

 afterwards the spotted surface disintegrates and small holes are formed. 

 Thus the presence of Psylla mali in the adult stage can easily be recog- 

 nised. Another class of insects (Jassids) also produces white spots, 

 but these can be easily distinguished from those of Psylla mali by mere 

 observation. 



(c) Flight. They are rarely seen on the wing unless disturbed. 

 Then they seem to jump forward with their hind legs and take a short 

 flight — from leaf to leaf or twig to twig. 



{d) Habitat. Psylla mali seem to choose the under surface of 

 leaves, though they are sometimes found on the upper. In the adult 

 stage they are not confined to apple trees alone, but seem to migrate to 

 different plants interspersed with the apples. They are found on 

 gooseberry bushes, pear trees, plums, etc., besides apple trees. This 

 migration may explain how the infestation is carried from one orchard 

 to another, because their powers of flight would not sustain them in 

 direct migrations from one apple-orchard to another. 



Ann. Biol. i. 1*^ 



