234 [September, 



(fig. i), while in some of the feebly-marked rufa forms it is decidedly concave (fig. 

 5). The scape of the feeler, which in many rufa males is entirely black, as in the 

 queens, may show a yellow patch as large as that which characterizes austriaca 

 (fig. 3). The males of F. rufa vary much more than the females. It is remarkable 

 that no queen or worker of V. rufa examined by us shows any trace of yellow on 

 the scape of the feeler, but of twenty-eight queens of V. austriaca, five have the 

 usual yellow mark very faint, and in two the scape is entirely black as in F. rufa. 

 Further, some austriaca queens, taken at Bray by Mr. Barrington during the 

 present year, have a black trident-mark exactly like that of the rufa male (fig. 5) 

 referred to above. 



Turning next to the abdominal segments, we find that the basal segment of 

 F. austriaca is, in many cases, not longer absolutely than that of F. rufa, but that 

 it only appears so, because the segment in F. rufa is always broader than in F. 

 austriaca. Some specimens of the former wasp have, however, the basal segment 

 narrower than usual (fig. 13), and some examples of the latter have it broader than 

 usual (fig. xiii). There is thus a tendency in each of the forms to vary in the 

 direction of the other ; yet the narrowest rufa abdomen we have measured is 

 broader than the broadest of austriaca. Viewed in profile, the front slope of the 

 basal segment in F. austriaca is steeper than in F. rufa, though here also there is 

 some amount of variation (compare figs. 14, 15 with figs, xiv, xv). We notice that 

 the black markings of the abdominal segments are relatively broader and more trun- 

 cated in F. austriaca than in V. rufa (figs. 12, 13, and figs, xii, xiii), but we possess 

 queens of either form showing the abdominal markings of the shape characteristic 

 of the other. In the typical specimens of V. austriaca, the black abdominal mark- 

 ings stand out clear and sharp on the lemon-yellow ground ; but fully 25 per cent, 

 of the males of this wasp examined by us show a decided rufous tinge around the 

 black, and in some this is so marked that an examination of the shins or the male 

 armature is necessary before the specimen can be satisfactorily determined. On the 

 otlier hand, some specimens of F. rufa show hardly any trace of the rufous tinge. 



It is believed by most students of the Hymenoptera that the male armature 

 furnishes characters exceptionally reliable for the discrimination of species. In F. 

 austriaca the appearance of the organs generally is narrower, more parallel-sided, 

 and paler than in V. rufa (figs. 1, i), as was remarked by Robson ('98). Looking 

 at the details of the armature, we find that there is a fairly constant difference in 

 the form of the stipes (fig. 6, vi, st.), and that the appendage at its tip is narrow in 

 F. rufa, ending in a very slender flexible point (fig. 6, b, fig. 8), but broad and pro- 

 minent in F. austriaca, ending in a straight and more rigid point (fig. vi, b, fig. 

 viii). But in this character, again, there is occasionally a tendency in each species 

 to vary towards the other (compare figs. 9 and 10 with figs, ix and x). And it is of 

 special interest to find that this variation in the armature sometimes (not by any 

 means always) accompanies the variation in the face-markings. Figs. 3 and 9 have 

 been drawn from one aberrant male of V. rufa, figs. 4 and 10 from another ; figs, 

 iii and ix from one aberrant male of F. austriaca, figs, v and x from another. A 

 detail of the armature which seems fairly constant is the process of the inner face 

 of the stipes ; this is longer and narrower in F. rufa than in F. austriaca (figs. 6, 

 a, vi, a, 7, vii), and exhibits very little variation in either form. 



If the armature of the males of our native wasps be compared, there can be no 



