638 



The Apple Blossom Weevil. 



[Oct., 



that it was thought advisable to spend a considerable time 

 in working out the details and in studying control methods. 

 This work has been in progress at the Agricultural and Horti- 

 cultural Eeseareh Station, Long Ashton, since September, 1920, 

 and the following is a summary of the results. 



Life History. — Towards the end of March the weevils leave 

 their winter quarters, and, warmed by the sun, crawd to the 

 smaller branches of apples and pears, and piercing the blossom 

 buds as soon as they show green at the tips, thrust the rostrum, 

 01 trunk, downwards towards the growing point and suck the 

 juices. It is at this period that the use of the "V" mark 

 on the elytra is important for the weevils are very much 

 exposed to the attacks of birds. This mark splits up their 

 outline and affords considerable protection as shown at A, 

 Fig. 1, where the weevil fits the colours in with its immediate 

 surroundings. This spring feed stimulates the sexes and 

 mating takes place. iVlternate periods of feeding and resting 

 in any available shelter now extend until the blossom buds 

 reach that stage of development known as the " Cluster-bud " 

 stage, i.e., when the first young leaves bend outw^ards reveal- 

 ing the individual flower buds in a compact cluster (A, Fig. 2). 

 This stage is usually reached within five weeks after the first 

 appearance of the weevils — in 1922 the weevils were first seen 

 feeding on 23rd March and the ' ' cluster-bud ' ' stage was 

 reached by 28th x\pril. Egg-laying now takes place; the 

 female selecting a flow^er bud proceeds to drill a hole into it 

 with her rostrum which penetrates calyx and petals and 

 scoops a hollow cavity in the anther lobes. This operation . 

 takes about ten to twelve minutes, after which the female 

 reverses her position and thrusting her ovipositor into the 

 hole deposits an egg in the prepared cavity in the anther. 

 This takes from one to two minutes. The cavity is not closed 

 up with saliva as was formerly thought but by the congealing 

 of a sappy exudate from the damaged tissue of the calyx. 

 After about eight to thirteen days the eggs hatch and the young 

 larvae or grubs commence feeding on the pollen cells of the 

 anthers. Feeding goes on for a fortnight to three weeks 

 during which time the anthers, filaments and styles are de- 

 stroyed, and often the surface of the receptacle is damaged. 

 The larvae gnaw at the base of the petals with the result 

 that the petals do not open in the ordinary way but dr}' and 

 form dome-shaped coverings under which the larvae live. 

 These are known as " capped " blossoms. Several moults 



