258 Ap2)le and Pear Sucker 



a single bud. Each larva thrusts its stylets deep into the tissues and 

 begins sucking the juices. The suction-pumps of the larvae are at 

 work night and day sucking the juices of the bud until it completely 

 dries up. The leaves become brown, as if they were frost-bitten, wither, 

 and drop down one by one. The buds, both floral and foliage, are thus 

 destroyed wholesale and the apple trees cannot, of course, bear any 

 fruit. If there is any remedy to be applied, it should be applied when 

 the insect is in the larval stages. It seems that the growth of the buds 

 (floral and foliage) runs parallel with the development of the Psylla 

 mail. Soon after the flowers are set, Psylla mali is in the adult stage, 

 when it does no damage. There are other effects produced indirectly 

 by these larvae. They soil the bud-leaves by the secretion of waxy 

 substances when the threads of secretion are broken up. The trans- 

 lucent stuff of the core exudes and covers the surface of the leaf. Par- 

 ticles of dust get glued to the leaf. In fact the wax forms an impervious 

 layer over the surface. This may interrupt free transpiration of the 

 leaves, which may thus be smothered and suffer. It is, however, curious 

 that no fungus is seen growing on the leaves thus wetted by the larvae. 

 This effect is not universal and may only be found in some places. 



VI. The Adult. 



(a) The external sexual differences, (i) Both sexes seem to be alike 

 in general appearance, though there is an obvious difference in the shape 

 of the genitalia. In the male they are curved and turned upwards, 

 while in the female they are straight and pointed and lie concealed in 

 the upper and lower anal segments. Their anatomical description in 

 the female only will be given below in the reproductive system. 



(ii) Colour differences. The colour of the male seems to be brown 

 or at the most pale green ; it is never green nor deep green ; while the 

 females are nearly always deep green. The colour in both the sexes 

 changes with the age of the insects, but it never becomes uniform in 

 both the sexes. 



(iii) Abdomen. The abdomen of the female seems to be broader 

 when it is fertilised, while that of the male is very narrow and 

 tapering. 



(6) The proportion of the sexes. In the beginning of this investi- 

 gation it was suspected that there was parthenogenesis among these 

 insects. If so there would be a disproportion among the sexes — the 

 females outnumbering the males. To solve this question the adult 

 insects were caught at different times from the period they emerged from 



