OF WASHINGTON. 305 



of the Sphegidcc, with smooth legs, near Pelopaeus, as appears 

 by a note attached to a specimen of the type in the collection of 

 the British Museum. [Note. Antennas focm. not geniculate ; 

 hind wings incised at end of the pobrachial vein ; fore wings 

 with a third discal areole. See also form of thorax. I think a 

 sphegid with smooth legs, near Pelopaeus. Haliday MS. in 

 Brit. Mus.]" 



Prof. Westwood on exhibiting a specimen of this insect at a 

 meeting of the London Entomological Society recognized it as a 

 new genus of Aculeates, with most perplexing structural affinities, 

 but thought that it came closest to the family Vespidas, although 

 the male, in its elongated antennae, was not unlike an ant. 



Mr. F. Smith, on the same occasion, also considered that " it 

 had more characters in accordance with those of the ants than 

 with any other family." (Proc. Ent. Soc., Nov. 16, 1868.) 



Prof. Westwood says, further, that Mr. Cresson, who first 

 described this genus, placed it undoubtingly amongst the multi 

 tudinous genera of the Ichneumonidce (which caused me to 

 overlook it), remarking, "I am at present unable to define the 

 true position of this remarkable genus. It seems to form a con 

 necting link between Ichneumones genuini and the Adsciti '/ 

 from the former it differs by the paucity of the antennal joints, 

 and from the latter by the anterior wings having a faint indica 

 tion of a second recurrent nervure. Its structure places it, beyond 

 doubt, in the family Ichneumonidce, whilst its general appear 

 ance, together with the arrangement of the wing-veins, seems to 

 place it among the Adsciti, where I will allow it to remain for 

 the present." 



Subsequently, Mr. Smith (without being aware that the insect 

 had been thus commented upon by Mr. Cresson), in a paper 

 communicated to the Entomological Society on the 4th Jan., 

 1869 (Trans. 1868, Proc. p. li), discussed the affinities of this 

 genus at length with great acumen, contending, " ist, That all 

 wasps have the wings folded, whilst they are flat in Rhopalosoma. 

 2nd, Rhopalosoma has only two submarginal cells, whilst every 

 known wasp has either three or four. 3rd, Every true wasp has 

 three discoidal cells in the fore-wings, whilst Rhopalosoma has 

 only one. 4th, The prothorax (collar) in all Vespidas extends 

 backwards to the tegulaa, which is not the case in Rhopalosoma. 

 5th, Lunate eyes (which Rhopalosoma possesses) are found in 

 Mutilla, Scolia, Sapyga, Pemphrcdon, and Philanthus 

 amongst the Aculeata, and in the Ichneumonideous genera 

 Pimpla, Campoplex, Anomalon, Ophion, and some others. 

 6th, The tarsal ungues (toothed in Rhopalosoma) are simple in 

 the social Vespidas, although dentate in the solitary wasps." On 

 the other hand, Mr. Smith regarded the insect as belonging to the 



