ON THE BIOLOGY OF THE APPLE SAWFLY, HOPLOGAMPA TESTUDINEA KLUG.

Abstract

SUMMARYThe biology of the apple sawfly, Hoplocumpa testudinea Klug., has been under observation for several years in the north‐west of England. Mating and oviposition are described and an account is given of the position of the eggs on the host plant. Usually the eggs are found under the epidermis of the upper surface of the receptacle within the calyx ring, and often within the bases of the stamens.The incubation period normally varied from 8 to 15 days. During this period the eggs increased slightly in size, and the majority ruptured the epidermis of the receptacle and so became partly exposed within the calyx ring.The larvae emerge from the eggs on the outside of the fruitlet and proceed to penetrate it either from within The calyx ring, or by passing over the calyx on to the side of the receptacle and tunnelling in from that position. It appears that the larvae seek the ovary but numbers never reach it, and at this stage there may be some mortality among the larvae.Larvae which reach the ovary feed for a short time on the developing seeds and at about the third instar migrate to older fruits. Circular or ribbon scars appear to be caused by the wanderings of first instar larvae in their first penetration of the fruit.The larvae are described. They have five instars and a growth ratio of about 1.4. They measure 9–11 mm. when mature.The larvae over‐winter in cocoons, the majority of those under observation were constructed a t a depth of 3–9 in. in the soil. The pupal period lasts 3–4 weeks.Notes are given on infestation by apple sawfly in relation to variety and date of blossoming of a number of apple varieties, and the significance of details of the biology of the species on control measures is discussed.