F. R. Petherbridge and M. A. Husain 193 



Habits. 



Plesiocoris rugicolUs hatches out after the buds of the apple have 

 opened and about 16-17 days before the flowers are in full bloom. Very 

 soon the young larvae move to the opening buds and begin to feed on 

 the tender opened or half-opened leaves which at this stage are not more 

 that about an inch in length. On the opened leaves they usually feed from 

 the upper surface more especially on each side of the mid-rib of the basal 

 half of the lamina (see PL XI, fig. 12). They also feed on the upper surface 

 of the rolled opening leaves and here they are partially concealed. Every 

 leaf where they feed soon shows the characteristic brown spots. On being 

 disturbed they run away very quickly and conceal themselves either in 

 the curled leaves or the axils of the opened leaves. It is difficult to shake 

 them off a branch at this stage, even when falling from one of the upper 

 branches of a tree they hardly ever reach the ground but obtain a hold on 

 one of the lower twigs either by means of their sharp claws or by ex- 

 truding the posterior part of their alimentary canal which secretes a 

 sticky fluid. The hairs on the leaves and stems of the apple seem to help 

 them in regaining their hold as they are more easily shaken off the black 

 currant. The later instars are more easily shaken off. At all stages they 

 run very quickly but seem to be more active during the younger stages. 

 They dodge like a squirrel by running to the opposite side of the stem 

 and it is often difficult to catch them. 



They share with other insects the habit of cleaning their antennae by 

 means of the hairs at the ends of the front tibiae after which they often 

 rub their tibiae against each other. They moult in any situation, cast 

 skins having been found on both surfaces of the leaves, on the petioles 

 and on the stems. When ready to moult they become very sluggish and 

 stop feeding. Moulting takes place by a longitudinal slit in the mid- 

 dorsal region of the thorax, this being preceded by a throbbing in the 

 region of the callosities on the pronotum. The thorax and part of the 

 head and abdomen come out first, followed by the legs and antennae and 

 lastly by the rostrum. After moulting the bugs feed voraciously, making 

 repeated stabs at the leaf at the rate of about fifty per hour. 



The adults are easily shaken from the trees. 



In walking through an infested orchard we have never seen them flying 

 from one tree to another, but they can fly a fair distance when disturbed. 

 When shaking them from a tree into a Bignell beating tray they often 

 fly back again into the tree before reaching the tray and some of those 

 which reach the tray fly back to the tree again. In the laboratory they 



