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the methods of breeding and collection described. All the instars, 

 except the fifth, are gregarious in habit. Infested buds can be easily 

 recognised by the waxy threads hanging down from them. 



P. mali is most daiigerous to apple trees in its larval stages ; the 

 adults doing practically no damage. The leaves wither and the buds 

 are destroyed wholesale. All remedies should be applied when the 

 insect is in the larval stage. Soon after the flowers are set, P. mali 

 is in the adult stage, when it does no damage. The different catches 

 observed, did not indicate any great disproportion in the sexes or 

 any evidence of the existence of parthenogenesis. The change of 

 colour in the adults is described. The presence of P. mali in the 

 adult stage can easily be recognised by the minute circular, white 

 spots with which the leaves are marked ; these spots are caused by 

 the sucking of the juices and seem to increase in size, and later the 

 damaged surface disintegrates and small holes are formed. The adults 

 are rarely seen on the wing unless disturbed, when they take a short 

 flight from leaf to leaf or twig to twig ; they usually occur on the under 

 surface of the leaves. They migrate to other plants near apple 

 trees and are found on gooseberry bushes, pear trees, plums, etc. 

 This may explain how infestation is carried from one orchard to 

 another, as their powers of flight would not suffice for direct migrations 

 from one apple-orchard to another. Both tracheal and reproductive 

 systems are described and figured, and it is suggested that the former 

 organs deserve more attention, as they are the chief medium through 

 w^hich a contact poison acts. The egg-laying season only extends over 

 a week, in the first half of September. The adults are found as late as 

 October and appear to die towards the end of that month. Except 

 for some red mites, no enemies of P. mali were observed. 



P. pyricola (pear-sucker) is the most important pest of pear trees on 

 the Continent and in America, and has recently been found in the 

 United Kingdom. It has a similar life-histoiy, but there are many 

 important differences which make it more formidable. Anatomical 

 differences are briefly indicated. The larvae of P. pfjricola are always 

 embedded in the waxy secretion they exude, which wets the surface 

 of the leaf, but there are no white threads, nor are there white spots 

 on the leaves. On this secretion grows the injurious fungus, Clado- 

 sjjorium herbarium, the sooty mould. The larvae are always found 

 in the open surfaces of the leaves of the pear trees and suck the juices 

 of the leaves, which become curled and withered. P. pyricola is 

 injurious in both larval and adult forms, while P. mali is only harmful 

 in the larval stage. There are three generations, the first in April and 

 May; the second, June, July; and the third, August, September. 

 The adults of the third generation pass through the winter and lay 

 eggs in the following spring when the females are fertilised. 



Experiments w^ere made to find a fluid which would penetrate 

 the waxy secretion, thoroughly saturate the bud leaves, and so 

 reach the larvae. A solution of 10 lb. soft soap in 100 gallons of 

 water was found to be a satisfactory solvent, but this will only 

 kill the larvae when it dries instantaneously, and in one experiment 

 28 per cent, were living after one spraying, mainly those on leaves 

 not exposed to the wind and sun. In order to obtain some poison 

 which would facilitate the action of the soap solution, experiments 

 were made with other wax solvents : xylol, petrol, kerosene, acetone 



