EpJiialfiS.] BRITISH ICHNEUMONS. 31 



not short. Abdomen sessile and cylindrical, scabrous, at least twice longer 

 than thorax and generally bearing tubercles or rugosities ; its segments 

 generally elongate and always a})ically elevated £uid nitidulous ; basal seg- 

 ment parallel-sided, not shorter than broad and centrally canaliculate with 

 the spiracles before the centre ; apical ventral segment small and retracted 

 from the anus, of 9 longitudinally excised ; terebra at least as long as 

 the body, with the \alvulae more or less strongly pubescent and not 

 deflexed ; ^ valvulae shortly exserted and often stout. Legs subelongate, 

 very rarely dentate ; apical tarsal joint twice or thrice longer than the 

 penultimate ; claws curved, not pectinate, of 9 lobately dilated at the 

 base. Wings not broad ; areolet irregularly triangular, sessile or sub- 

 petiolate, emitting the recurrent ner\aire from beyond its centre ; radial 

 cell narrow and elongate. 



Thomson very truly says (O. E. viii. 737) that this genus stands so close 

 to Pimpla in the conformation of its species that no exact line of demar- 

 cation can be found between them. In general, however, the species may 

 be known by the parallel-sided and cylindrical abdomen, which is not 

 c-oarsely punctate and always has the apices of the segments broadly 

 nitidulous, elevated and transaciculate, the 9 has the sixth to eighth seg- 

 ments transverse and the $ the second strongly elongate ; the flagellum 

 is alwavs entirely black with the joints of uniform breadth throughout, 

 though not distinctly discreted ; the eyes are not unusally prominent, the 

 vertex is broad, the clypeus apically emarginate or excised and the terebra 

 is not deflexed and thicker than in Pimpla. 



As in Rhyssa, the males of this genus are much rarer than the females. 



The large and conspicuous members of the present genus very early at- 

 tracted the attention of entomologists and the observations of some of 

 these, though too vague as to the actual species referred to, must not be 

 altogether omitted, especially since the economy and habits of the whole 

 group are probably identical. As long ago as 1741, Reaumur (JNIem. vi. 

 304) perceived one of "the ichneumons, at the instant it alighted on the 

 spot under which so many of the little green caterpillars had been stored 

 up by the wasps. Its long tail it carried horizontally. ... It moved its 

 ovipositor so as to bring it into a bent position under the body, protruding 

 it even beyond its own head ; taking care to direct it into the barricadoed 

 nest of the mason wasp. But although the insect appeared not to be dis- 

 turbed by my observations, yet I was unable to perceive whether the 

 toothed portion of the borer was pushed beyond the sides of the sheath. 

 What I did see, however, convinced me that the instrument was worked 

 in a manner well adapted to make its way through the mortar; for she 

 turned it half round alternately from right to left and left to right, as a 

 carpenter would his bradawl, and employed altogether more than a quar- 

 ter of an hour before she succeeded in penetrating to a suflicient depth." 

 I quote from James Rcnnie (Insect Transformations, 1830, p. 57), who 

 adds that " all thi- careful stratagems of the mason wasj) ( Odvncrus mura- 

 lius, L.) often prove ineffectual in guarding against the insidious intrusion 

 of a common ichneumon il}- {Pimpla maiiifis/a/or, (irav.) easii^• known by 

 its being black, with the legs red." (!)... " She waits patiently till the 

 wasp, having laid in a store of caterpillars for the young one, closes up 

 the do(jrway with a barricado of kiu-aded clay. It is this very barricado 

 which the ichneumon determines t(j assail in order to find a nest ready 

 prepared and slocked with |)ni\isi(iiis for her own progeny." 



