PTEROMALIDAE OF N.W. EUROPE 811 



see Muesebeck et al., 1951, and Peck, 1963. Several synonyms of cavus, other than 

 those cited above, are given by these authors. Some of them refer to American 

 species which I have not been able to examine ; consequently I have not included 

 them here as definite synonyms of cavus although in all probability they are so. 

 My chief concern here is to designate a lectotype for cavus ; also to give a short 

 redescription of the species, which is desirable in order to indicate the differences 

 between the nominotypical form and certain others (such as boarmiae) which may 

 be specifically distinct. 



Type material. Diplolepis microgastri Bouche. Types presumed lost ; there is 

 no mention of them in Sachtleben's report (1944 : 65-76) on the remains of 

 Bouche's collection in the Deutsche Entomologische Institut. 



Pteromalus cavus Walker. The syntypic series comprises 1 $ and 6 $, all labelled 

 " Pteromalus cavus Walker. Stood under this name in the old B.M. collection. 

 C. Waterhouse ". Two of the females may belong to a different species from the 

 rest. LECTOTYPE, the last specimen in the series, a female. It agrees well with 

 specimens bred from Apanteles on Pieris brassicae L. [see new records below] ; the 

 original description of cavus mentions (Walker, 1835 : 478) " Pontia [=Pieris] 

 brassicae " as a host. 



Pteromalus decedens Walker. Syntypes, 4 $, 7 $, all bearing Waterhouse labels. 

 LECTOTYPE, the ninth in the series, a female ; it is very close to the lectotype of 

 cavus and I consider it to be within the range of variation of that species. 



Pteromalus perversus Walker. One male stands under this name and is certainly 

 the TYPE (probably holotype) ; it bears a Waterhouse label. The gaster is broadly 

 oval and slightly pointed apically ; this explains Walker's supposition that it was 

 a female. It is a very small (length 1-35 mm.) very dark specimen which comes 

 extremely close to some males of cavus in the Oxford collections which were bred 

 from Digonochaeta setipennis Fin. (Dipt., Tachinidae), although the head appears 

 rather more transverse. I regard it as probably within the range of variation of 

 male cavus. 



Pteromalus tenuis Ratzeburg and P. boucheanus Ratzeburg. Types, formerly in 

 Ratzeburg collection, Eberswalde, now presumed destroyed. P. tenuis was later 

 stated to be conspecific with boucheanus by Ratzeburg himself (1848 : 189) and 

 there seems to be no reason to doubt the correctness of his conclusion. Thomson 

 (1878 : 161) recognized boucheanus as a Dibrachys, citing cavus as a probable 

 synonym ; his specimens seem to bear out this conclusion. 



In addition to characters mentioned in my key to species (see below) cavus has the 

 following, as seen in specimens from southern England. 



$. Head and thorax bronze, dark bluish, or dark greenish blue. Antennal scape (Text-fig. 

 666) often entirely fuscous, but sometimes testaceous proximally, rarely mainly so ; pedicellus 

 and flagellum usually fuscous to black, occasionally the pedicellus paler beneath. Wing veins 

 varying from brownish testaceous to almost white. Legs variable in colour, from almost 

 entirely black to extensively testaceous ; in those having the palest legs only the coxae are 

 black, the remainder being testaceous with the femora and tibiae slightly brownish. The tarsi 

 are sometimes mainly testaceous but are more often mainly brown or fuscous. Marginal vein 

 2 0-2 9 times as long as the stigmal vein ; postmarginal usually as long as or even very slightly 



