340 HYMENOPTEKA. 



this latter has no keel. The abdomen is longer than the head and thorax together, 

 and becomes gradually narrowed towards the apex. The tibiae and tarsi are densely 

 covered with pale hair ; the apices of the four front tarsi are black. 



16. Iphiaulax imitatrix. (Tab. XIV. fig. 13, $ .) 



Long. 12 millim. ; terebra 11 millim. 



Hab. Panama, Bugaba (Champion). 



I am not quite sure but that this is only a form of /. championi ; the chief distinction 

 lies in the form and structure of the abdomen : it is a little shorter and broader ; the 

 petiole is much more vertical, its top being higher than the mesonotum, while in 

 I. championi it is lower, and is almost on a level with the rest of the abdomen ; there 

 is neither depression nor keel on the fourth segment, while in I. championi there is in 

 its centre a large depression, with a keel down the middle, like that on the third, only 

 narrower ; the fifth segment in I. championi has also a depression. In coloration the 

 two are almost identical. The clouds in the wings are much darker in I. imitatrix 

 than in I. championi. 



The occurrence of these two forms in the same locality makes me think that it is 

 possible there may be some variation in the furrows, keels, &c. on the abdomen, or 

 rather that in some individuals these parts may, through immaturity, be much less 

 developed than in others. This is a point, however, which can only be tested by the 

 examination of a large series of specimens. 



The group of I. gloeiatoeius. 



Keel on the second segment triangular, bordered by a deep and wide furrow ; the lateral 

 furrow oblique ; a deep fovea on either side of the apex of the petiole. Suturiform 

 articulation narrow, impunctate; the apical branch roundly curved, reaching to 

 near the middle of the segment, which is contracted in the middle above. Abdomen, 

 if anything, shorter than the head and thorax united. The curve of the oral region 

 wide, of nearly equal depth throughout, the centre of the clypeus being but slightly 

 emarginate ; above the latter is a rather deep Ci-shaped indentation. Luteous ; the 

 head, the prosternum, the apex of the abdomen, and the greater part of the legs, 

 black. (Species 17 & 18.) 



In coloration this group agrees with that of I. sciarius and I. championi ; from the 

 former (which it resembles in the form of the suturiform articulation) it differs in the 

 keel on the second segment being triangular ; from the latter in there being no keel on 

 the third segment ; and from both in the clypeal incision being much less strongly 

 marked. 



