n8 M. W. R. de V. GRAHAM 



For designation of lectotypes, and discussion of the synonymy of the other species 

 (except lappa) see Kerrich & Graham (1957 : 300-302). 



Trigonoderus linearis is a small slender form with very dark legs ; it may be a form 

 of ductilis, though I have found small differences which suggest that it might be a 

 valid species. Further study of the range of variation in ductilis is necessary to 

 settle this question. 



Trigonoderus lappa Walker. Lectotype $ designated by Kerrich & Graham (1957 : 

 303), who placed it in synonymy with dolosus (Walker). It has the striate sculpture 

 of the scutellum rather similar to that of male dolosus but its antennae are quite 

 different. It certainly belongs either to ductilis or to affmis. 



Britain, Sweden, ? Czechoslovakia. 



Biology. Because ductilis (Walker) and affmis (Walker), regarded by Kerrich & 

 Graham as forms of one species, are now considered to be distinct, it is difficult to be 

 sure which host-records apply to the true ductilis without re-examining the speci- 

 mens. The record given by Kerrich & Graham (1957 : 301) under forma deductor 

 refers to true ductilis (England, Berkshire, Windsor Forest, 19. iv. 1933, a female 

 taken from burrows of Ips (=Tomicus) suturalis Gyll. in spruce bark). Szczepahski 

 (1961 : 5) recorded ductilis as a parasite of Scolytus ensifer Eichh. in Poland ; but his 

 species was probably not the true ductilis. Walker (1836 : 18) recorded ductilis as 

 occurring " May and June ; on posts and beams of wood perforated by Anobium, 

 etc. " During May 1963, in my garden in Oxford, I observed males and females of 

 ductilis walking about trellis-work made of old Corylus twigs which were heavily 

 infested by Anobium punctatum DeG. ; it seems very likely that they were 

 parasitizing this beetle. On 29.V.1968, at Southgate, Middlesex (which is probably 

 the type-locality for this species) I captured a $ ductilis as it was investigating holes 

 made by Anobium, on the bole of a decaying Salix fragilis. Imagines appear in 

 May and June. 



Platygerrhus affinis (Walker) agg. 



Trigonoderus affinis Walker, 1836 : 19, <j>. 



Trigonoderus amabilis Walker, 1836 : 20, 9, syn. n. 



? Pteromalus (Pterolycus) Gravenhorstii Ratzeburg, 1852 : 245, $. 



Platygerrhus gracilis Thomson, 1878 : 14, $, syn. n. 



Trigonoderus ductilis f. affinis (Walker) Kerrich & Graham, 1957 : 300, 301. 



? Platygerrhus millenius Szczepahski, 1961 : 5-10, 0* ?• 



Type material. For designation of lectotypes for the above species, and discussion 

 of synonymy, see Kerrich & Graham (1957). In that paper the names here cited 

 under affinis were regarded as synonyms of ductilis (Walker) . 



Pteromalus {Pterolycus) gravenhorstii Ratzeburg. Types presumed destroyed. 

 The species was thought by Novitzky to be a Platynocheilus, but in an earlier paper 

 (Graham, 1963, Trans. Soc. Brit. Ent. 15 (9) : 169-170) I gave my reasons for thinking 



