208 SCIENCE PROGRESS 



Hymenoptera. — Brues {Am. Nat. 55, 134-64) contributes 

 an interesting survey of parasitism among Hymenoptera, with 

 particular reference to the relation between taxonomic affinities 

 and methods of feeding. The complete life-histories of three 

 Chalcid ectoparasites of Harmolita tritici have been followed by 

 W. J. Phillips and F. W. Poos (Journ. Agric. Res., June 15, 192 1). 

 (Miss) M. Haviland {Q.J. M.S., 65, 101-127) has supplied a 

 careful account of the biology of two species of Lygocercus, 

 which parasitise the Braconid Aphidius. It is a useful con- 

 tribution to what little is known of the economy of the Scelioni- 

 dae. A. C. Kinsey {Bull. Am. Mus. Nat. Hist., xlii, articles v- 

 vii) writes on American Cynipidse. In article vii the author 

 estimates that 86 per cent, of the known species of the family 

 affect Quercus and are confined to that genus. Another 7 per 

 cent, are confined to species of Rosa. The remaining 7 per cent, 

 occur on plants belonging to various natural orders, and it is 

 evident therefore that 93 per cent, of the known Cynipidae are 

 restricted to two plant genera only. The author concludes that 

 alternation of generations is a more or less extreme development 

 of seasonal dimorphism and is primarily due to seasonal environ- 

 mental conditions. L. M. Alston {Proc. Zool. Soc, 1920, 195- 

 243) has contributed a detailed account of the life-history of 

 two parasites of Calliphora erythrocephala. One of the species, 

 Alysia manductor, parasitises the larval host and its imagines 

 emerge from the puparia. This Braconid is a member of an 

 anomalous group which was elevated by Ashmead to the rank 

 of a separate family. The second species dealt with is the 

 Chalcid Nasonia brevicornis, which is a pupal parasite of the 

 Calliphora. G. Grandi {Boll. Lab. Zool. Portici, 14, 63-204) 

 has published a lengthy study of the morphology and biology 

 of Blastophaga psenes. It is by far the most thorough investiga- 

 tion of any Chalcid yet attempted, and is accompanied by a 

 remarkably complete bibliography, and a review of the subject 

 of caprification with which this species of Blastophaga is so 

 closely associated. 



Diptera. — G. S. Cotterrill {Proc. Zool. Soc, 1920, 629-647) 

 gives a much-needed detailed account of the metamorphoses of 

 the common yellow dung-fly Scatophaga stercoraria. It is 

 remarkable that so familiar an insect should never have been 

 adequately studied previously. D. Keilin {Parasitology, xiii, 

 180-83) contributes a further annotated list of larval Diptera 

 known to prey upon Mollusca. J. E. Collin {Trans. Ent. Soc, 

 192 1, 305-26) describes the various British species of Ham- 

 momyia and Hylephila which, it may be added, are closely 

 related to the cabbage-root fly and the onion-fly. Their biology 

 is of interest in that they are closely associated with solitary 

 bees, particularly of the family Andrenidae. The female flies 



