Zoology 75 



behind our knowledge of, say, the Coleoptera ; and an attempt to assess the 

 hymenopterous fauna of the County must, in the main, be regarded as 

 preUminary. 



The sawfly fauna' should be very rich, considering the abundance and 

 variety of willows, grasses, and horse-tails, the most characteristic food 

 plants of these insects ; and sawflies certainly are numerous in individual 

 species, particularly in the fen country. Mr Benson collected them energeti- 

 cally during his student days, but they have since received very little 

 attention; and, probably, the known total of 172 species could be nearly 

 doubled. Three Pamphihidae, five Cephidae, and five Cimbicidae are 

 known: a Cimbicid larva sometimes rewards a search on wHlows. 

 Xiphidria prolongata Geoffr. has several times been taken; and three 

 Siricidae are known, as are both their parasites, Rhyssa persuasoria L. 

 (Ichneumonidae) and Ibalia kiuospoides Hochenw. (Cynipoidea). Of the 

 Tenthredinidae, the occurrence of the rare Ametastegia albipes Thoms. is 

 especially interesting. 



For AcLileata, the County is much less favourable. On account of the 

 absence of sandy ground, except along two parts of the County boundary, 

 the numerous sand-living species are absentees or strays. The bees are the 

 group least affected; Adrenidae, in particular, are well represented, and 

 many of them visit wthow flowers in the spring. Bumble-bees are con- 

 spicuous both in and around the fens and in College gardens. An interesting 

 fen bee is the little Hylaeiis pectoralis F5rst., which nests in old reed galls 

 of the fly Lipara luceiis Mg. Its parasite is Gasteruption rugtilosttm Ab. The 

 best distributed ant is Acatithomyopsflavus Fabr. The hornet, Vespa crabro L., 

 nests in old wUlows and old cottages. Cleptes semiauratus L., a sawfly 

 parasite, is fairly common; and the Chrysididae are well represented. 

 Several of these latter belong to the interesting fauna which frequents old 

 posts, including species nesting therein, and their parasites. There are 

 many such posts along the approaches to Wicken Fen, and these have 

 frequently been studied. The commonest species is Trypoxylon jigulus L.; 

 Sapyga clavicomis L., and the rare Cuphopterus cotifusus Schulz, recendy 

 discovered there by the late H. P. Jones, may also be mentioned. The 

 species total of Aculeata for the County, excluding the Gamlingay 

 district, is 236. 



Of the gall-wasps, ordy those living on Centaurea and Rosa have been 

 seriously studied. Isocolus scabiosae Giraud and fitchi Kieff., Rhodites 

 spinosissima Giraud and mayri ScUechtd. have not been found; but the 

 other known British species occur in the County, as do the two PericUstiis 



' I wish to thaiik Mr R. B. Benson for giving me access to the manuscript of his 

 section on sawflies for the account in the Victoria County History of Cambridgeshire. 



