211 



OBSERVATIONS ON PIMPLA POMORUM RATZ., 



A PARASITE OF THE APPLE BLOSSOM WEEVIL 



(INCLUDING A DESCRIPTION OF THE MALE BY 



CLAUDE MORLEY, F.Z.S.). 



By a. D. IMMS, M.A., D.Sc, 

 Reader in Agricultural Entomology , Manchester University. 



(With Plate XII and 5 Text-figures.) 

 CONTENTS. 



PAGE 



1. Introductory Remarks . . . . . .211 



2. The Female 212 



3. The Male 213 



4. Observations on the Biologj^ of the Species , . .214 



5. The Young Larva 217 



6. The Fully Grown Larva 218 



7. Comparison with Larvae of other Ichneumonoidea . . 220 



8. The Male Pupa 222 



9. The Female Pupa 223 



10. Efficiency as a Parasite 223 



11. Remarks on other Parasites of J /i//(0/io?H?/s ^)o?;io;-«m. . 225 



12. Summary of General Conclusions ..... 225 



13. References to Literature 226 



14. EKplanation of Plate 227 



1. INTRODUCTORY REMARKS. 



Towards the end of May, 1916, I received several consignments of 

 apple blossom buds attacked by Anthonomus pomoriim. These were 

 kindly sent at my request by Mr J. C. F. Fryer, Entomologist to the 

 Board of Agriculture, who obtained them from an orchard at Chatteris, 

 Cambridgeshire, where the weevil is often abundant. It is a well-known 

 fact that A. jpomorum is a most difficult pest to control on account of its 

 concealed habits of feeding when in the larval stage, which greatly mili- 

 tates against the effective application of insecticides. The female weevil 

 deposits her eggs in the blossom buds of the apple before they open, 

 and, according to Theobald (1909, p. 106), the young larvae hatch out in 

 from 5-7 days. The blossoms commence to expand but rarely fully open, 

 further growth ceases, and the brown shrivelled petals form a kind of 

 dome-like cap over the receptacle. If one of these so-called "capped 



