SOCIAL WASPS AND HORNTAILS 79 



Vulgaris and rufa carry on the clypeus a vertical black 

 stripe, descending, in the workers, from the centre of its 

 upper edge to the centre of the lower, and more or less 

 dilated near the lower extremity into two lateral projec- 

 tions. In the males and females the mark usually does 

 not quite reach the lower margin of the clypeus, but 

 terminates at these projections, and it thus acquires 

 something of the appearance of a cheese-cutter with a 

 long and stout handle. It has also been likened, with 

 less justice, to an anchor, and hence both these species 

 are sometimes called anchor-faced wasps. Norvegica also 

 carries the anchor-mark on its clypeus ; so that there are 

 three species adorned in this way, two ground-wasps and 

 one arboreal species. 



Germanica, on the other hand, carries in the workers 

 a central black stripe, stretching only part of the way 

 down the clypeus, and often more or less imperfect, and 

 two black dots placed triangularly with the free end of 

 the stripe. In the males and females, there are usually 

 simply three black dots, placed triangularly, without a 

 black stripe at all. Lastly, sylvestris has only a single 

 black dot in the centre of the clypeus, or, in the females, 

 often no black markings at all. 



Turning now to the basal segment of the abdomen, 

 we find that rufa has some rusty stains around the black 

 spots there, in addition to the yellow band which occupies 

 the greater part of the segment ; and the same rusty hue 

 often occurs on other segments as well. It is from this 

 peculiarity that the species derives its name (rufa = red). 

 But it would not be safe to conclude that any anchor- 

 faced, red-spotted wasp is rufa, since norvegica is usually 

 similarly coloured; the red colour, however, will serve 

 to distinguish rufa from vulgaris, both of which, it will 

 be remembered, are anchor-faced. 



