Famity—EVANIID. 131 
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 Vespidw extends backwards to the 
tegulie, which is not the case in Rhopalosoma. 5th, Lunate eyes (which Rhopalosoma possesses) are found in 
Mutilla, Scolia, Sapyga, Pemphredon, and Philanthus amongst the Aculeata, and in the Ichneumonideous 
genera Pimpla, Campoplex, Anomalon, Ophion, and some others. 6th, The tarsal ungues (toothed in Rhopalo- 
soma) are simple in the social Vespide, although dentate in the solitary wasps.’ On the other hand, Mr. Smith 
regarded the insect as belonging to the Ichneumonides. ‘7th, Because, amongst the minute [Adscitous] groups, 
species exist having only 12-jointed antennw (Ephidrus), and others having 13-jointed antenne (Trioxys).’ 
8th, Mr. Smith states ‘that in Rhopalosoma a distinct second joint in the trochanters is quite as visible as in 
the Ichneumonideous genus Metopius. 9th, The antennex of every known species of wasp are geniculate, which 
is not the case in Rhopalosoma. 10th, The prothorax of Rhopalosoma is of the same structure as in Ophion 
and Anomalon. 11th, The ocelli are large and prominent in Rhopalosoma, as in the two last-named genera ; in 
the Vespide they are much smaller, and usually more sunken than prominent. 12th, The broadly dilated tarsi 
in Rhopalosoma do not occur in Vespidie, but are peculiarly characteristic of Anomalon, 13th, The basal seg- 
ment of the abdomen of Rhopalosoma is narrowed into a petiole, as in Ophion and Anomalon. 14th, The sting 
of Rhopalosoma agrees with that of Ophion and Anomalon, as well as Belonogaster and Vespa.’ 
Although thus pointing out the relationship of the genus with Ophion and Anomalon, Mr. Smith admitted 
its want of ‘strong affinity with any other known insect.’ 
To these objections I have to reply as follows :— 
. Some of the most aberrant wasp genera, and the remainder of the Aculeata, have flat wings. 
ore 
. Rhopalosoma has three submarginal cells. In all the genuine Ichneumons, the first submarginal and the 
anterior discoidal cells are thrown together. Even in those Adsciti which have three distinct sub- 
marginal cells, the first (and only) recurrent vein enters the first submarginal cell, and not the second, as 
in Rhopalosoma. 
3. Rhopalosoma has three discoidal cells, the lower outer one having its extremity partially closed by a transverse 
nearly obsolete vein. 
4, The collar of Rhopalosoma extends back laterally to the tegule, although not seen dorsally at the sides of the 
thorax. 
5. The eyes of Rhopalosoma are not lunate, but oval, with a small emargination in the middle of the inner margin. 
6. The ungues in Rhopalosoma are furnished beneath with two obtuse spines. 
7. No species of Adscitous Ichneumon, nor indeed any other terebrant Hymenopterous insect, is known 
possessing 13-jointed antenn in the males and 12-jointed in the females. This is one of the leading 
characters of the Aculeata. 
8. I cannot discover a second joint in the trochanters of Rhopalosoma. Its existence is one of the leading 
characters of the terebrant Hymenoptera. In certain positions, a faint appearance of an articulation 
near the base of the femora may be observed. In the Ichneumons the two joints of the trochanters 
are distinct, and nearly equal in size in many species. 
9. The long, straight, filiform structure of the antenne of Rhopalosoma is unquestionably a strong character 
against its belonging to the Vespidi. 
10. The front of the thorax of Rhopalosoma is similarly formed to that of Ophion. 
11. The ocelli of Rhopalosoma agree with those of Ophion. 
12. I know no Ichneumonideous nor indeed any other Hymenopterous insect with feet like those of the female 
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Rhopalosoma, whereas they are simple in the male. 
13. The pedunculated basal segment of the abdomen of Rhopalosoma occurs in many groups of Aculeata, as well 
as in many of the Terebrantia. 
14. The sting of Rhopalosoma is a genuine aculeus, with a broad sheath. 
15. The lobed base of the hind wing, and the 6-jointed maxillary palpi, which latter character occurs in no 
genuine Ichneumon, must not be overlooked in determining the relations of the genus. 
From the preceding discussion it will doubtless be considered that, whilst in several important respects the 
insect before us agrees with some of the Ichneumonide, it is, in others equally important, allied to the Aculeata, 
forming by itself a most exceptional and isolated section. 
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