Mesostenini.] BRITISH ICHNEUMONS. 259 



though its anomalous features render it more convenient at present to 

 treat of it in the position it has always hitherto held. 



Tabic of Genera. 



(2). I. Abdomen fusiform and broadly red ; thorax 



dull and punctate Mesostenus, Crav. 



(i). 2. Abdomen linear and not red ; thorax tjla- 



brous and nitidulous Nematopodius, Grav. 



Areolet of Mesostenus ligalor. Areolet of Nematopodius formosiis. 



MESOSTENUS, Graven/iorsf. 



Gr. I. E. ii. 750 (1829). 



Head short, transverse, posteriorly narrowed ; eyes oval and prominent ; 

 frons with no inter-antennal spine. Antennae longer and more slender 

 in $ . Thorax pilose, stout, punctate ; apophyses often stout and acute. 

 Scutellum convex, triangular, apically sub -obtuse. Abdomen smooth, 

 shining, convex ; basal segment somewhat curved, laterally margined ; 

 post-petiole sub-convex, often coarsely punctate ; second segment with 

 hind margin callose, the third apically depressed ; terebra deflexed and 

 longer than half abdomen. Legs elongate and slender. Wings normal ; 

 areolet small, rectangular, quadrate, emitting the second recurrent nervure 

 from its apical angle. 



Eighteen palaearctic species are known, an investigation of which would 

 probably extend our list from its present meagre proportions. Mesostenus 

 gladiator^ Scop., should certainly occur in Britain, whence it was errone- 

 ously recorded by Marshall in 1870 ; it is parasitic upon Ammophila, 

 Pelopaeus, Trypoxylon and Osmia, and differs very considerably from our 

 indigenous species in its entirely black body and very long terebra, bearing 

 similar facies to Cratocryptiis subpeiiolatus. I have already (Ichn. Brit. i. 

 220) mentioned that Mesostenus juai/ms. Marsh., has nothing in common 

 with the i)resent genus and is, in fact, referable to Phitylabus, Wesm. 



Table of Speeies. 



(4). I. Apophyses acute ; abdomen ov.ite ; second segment transverse 



(ME.SOSTENU.S, auctt.). 



(3). 2. Clypeus depressed ; segments flat 1. mc.ator, Grav. 



(2). 3. Clypeus convex ; segments convex 2. OMXOXIUS, Grav. 



(i). 4. Apophyses obsolete ; abdomen fusiform- 



linear ; second segment elongate 



(Stenaraeus, Thorns.) 3. Al.niNOTATUS, Grav. 



S 2 



