198 A Stndij of the Ccqjsid Buys found on Ap2)le Trees 



and comj)leted their development. They begin to feed more readily if 

 transferred in the early larval stages than in the later stages. Larvae from 

 apples also reached the adult stage when sleeved on black currants. In 

 an orchard at Great Eversden where for several years black and red 

 currants have been attacked, this year the rows of apples near them, 

 Worcester Pearmain, are also attacked. 



The black currant leaves are much thinner than apple leaves and 

 consequently the brown marks caused by the bugs soon fall out and 

 leave holes with a brown margin. 



Larvae of P. rugicoUis when sleeved on plum caused a few markings 

 but did not live long. The injury was similar in appearance to that of 

 black currant. 



Taylor (23) and Collinge(5) attribute the dimples in apple fruit to the 

 eggs of Lygus pratensis which are also laid in the stalk of the fruit which 

 may consequently fall of?. This is not the case with P. rugicoUis. 



Control. 



It has been shown by experiments (12, 12 « and some carried out 

 in 1917 by one of us) that P. rugicoUis can be kept in check by 

 spraying with " soft soap and nicotine." The amount of soft soap neces- 

 sarily varies with the hardness of the water, 1-0 per cent, or even less is 

 sufl&cient for soft water but it may be better to use more than this for 

 hard water. 0-05 per cent, of nicotine (98-99 per cent.) is sufi&cient. This 

 wash kills the bugs very quickly in all stages except the egg stage. 



In order to have its maximum effect the wash should be applied just 

 after all the bugs have hatched and spraying may continue for some time 

 after the fruit has become marked. It is necessary to spray with a 

 powerful jet and for this purpose a high pressure pump and a fairly coarse 

 nozzle should be used. The trees should be thoroughly drenched and 

 sprayed in a downward direction, keeping the nozzle fairly close to the 

 opening leaves. 



As the eggs are laid in the young shoots, trees from an infested nursery 

 should not be planted in non-infested areas. 



5. SUMMARY OF THE LIFE-HISTORY OF A CAPSID. 



Although these bugs do not undergo a sudden change at any moult, 

 yet each stage possesses characteristic features. The following is a brief 

 summary of these peculiarities founded on the study of the capsids dealt 

 with in this paper and others that have come under our notice and will 

 be applicable to a large number of species. 



