296 Bionomics of Weevils 



Parasites. 



Ectoparasite. On August 4th I observed two specimens of S. lineatus 

 each attacked by a mite which Mr S. Hirst has kindly examined for me. 

 He thinks it probable that the mite — which is a larval form — belongs 

 to the genus Trombidium or some closely allied genus. The mite occurred 

 under the elytra of the beetle, lying upon the fourth to the seventh 

 abdominal tergites, with its mouth-parts inserted in the body of the 

 beetle between the junction of the fourth and fifth abdominal tergites. 

 The mites were bright red in colour with pinkish legs and pale mouth- 

 parts. One measured 0-93 mm. long by 0-49 mm. broad, the other 1 -5 mm. 

 long by 0-84 mm. broad. The weevils they were found upon had been 

 collected from a bean field at Alness, Ross-shire, on August 2nd, and 

 were both old males that had emerged the previous autumn. Neither 

 seemed to be much the worse for the presence of the mite. 



Endoparasites. (1) Insectivorous. I have bred a considerable number 

 of the Braconid, Peril il us rutilus Nees from imagines of Sitones lineatus. 

 I have found this parasite to occur on S. lineatus both in the south of 

 England and in the north of Scotland. I am indebted to Mr G. T. Lyle 

 for his identification of this and the following species, and to Mr K. G. 

 Blair for passing on my inquiry to him. As I am at present engaged in 

 the investigation of the life-history and habits of this parasite I hope 

 to publish a complete account of it in a later paper. I have also bred 

 a few specimens of two other species of Braconidae from imagines of 

 S. lineatus collected in Suffolk by Mr B. S. Harwood. These are Pygostolus 

 falcatus Nees, the fuscous variety described by Ruthe, and Liophron 

 muricatus Hal, var. nigra. Both appear to be rarer parasites of S. lineatus 

 than is Perilitus rutilus Nees. 



(2) Fungoid. The most effective parasite of S. lineatus that I have 

 yet observed is a fungus Botrytis bassiana (Balsamo) Montagne, the 

 Muscardine of silkworms, which has been identified for me through the 

 kindness of Mr A. D. Cotton and Mr R. Beer at the Mycological Labora- 

 tory, Kew. This fungus is particularly common upon weevils of Sitones 

 kept under artificial conditions, but I have also observed specimens of 

 S. lineatus attacked by it in the field. It is always fatal to the weevil 

 attacked. While most easily observed upon the adult, I have proved 

 experimentally that it also causes death to the pupae and to the larvae 

 in all stages of development. Many experiments have already been 

 carried out on infecting the weevil with spores of the fungus both in the 

 laboratory and under muslin sleeves out of doors, all of which have 



