128 HYMENOPTEEA, 



base, and becoming narrowed and rounded behind, the apex projecting a little over the 

 metanotum. At the base of the metanotum and beneath the overhanging part of the 

 scutellum is a transverse carina, and from near the centre of this runs on each side a 

 curved keel to the side behind the posterior wings. The metathorax slopes down from 

 the scutellum, so that the thorax is much higher than the abdomen. At the apex of the 

 metathorax is a small round arc, separated from the following portion of the abdomen 

 by a white membraneous space, like the " blotch " of the Tenthredinidae ; this no doubt 

 representing the first abdominal segment, the abdomen being completely sessile. The 

 segment behind it is very large and slightly rounded at the apex ; the base being incised 

 by the large semicircular blotch. The rest of the abdomen tapers towards the apex ; it 

 is a little longer than the basal portion, and bears no trace of being composed of more 

 than one segment ; on the lower side, laterally, it is deeply incised, and from the upper 

 part projects the ovipositor. The ovipositor is nearly as long as the abdomen; it is 

 straight, broad, compressed laterally, and resembles the sheath of the Tenthredinidae. 

 Legs stout, tibiae slightly compressed. Anterior and posterior spurs very minute, and 

 seemingly single. Middle tibiae with one large, stout spur, longer than the basal joint 

 of the tarsus, and one short, stumpy one. Middle tarsi stout, thick, and setose on the 

 lower side. There is no marginal branch in the wings ; the cubitus is straight. 

 The remarkable structure of the abdomen distinguishes this genus at once. 



l. Aseirba caudata. (Tab. VI. fig. 13.) 



Nigro-caerulea ; flagello antennarum caudaque nigris, pedibus sordide testaceis, coxis et femoribus posticis 



caeruleis, femoribus tibiisque anterioribus proparte f uscis ; alis hyalinis. 

 Long, (cum terebra) fere 4 millim. 



Hal. Guatemala, Torola 1G00 feet {Champion). 



The antennae are longer than the head and thorax together, very slightly thickened 

 towards the middle, and covered with a fine pubescence ; the first joint of the flagellum 

 is not much more than half the length of the succeeding, which is the longest ; the 

 others become gradually (and slightly) shorter, and the apex is attenuated. The head 

 and mesonotum are semiopaque, and covered with a close, white, moderately long 

 pubescence. The sides of the pronotum and pleurae are very minutely punctured. 

 Abdomen smooth, shining, and sparsely pubescent; the ovipositor densely pilose, 

 opaque ; the head is covered with round, widely separated punctures. All the tarsi, the 

 tibiae at the apex, and the knees broadly, are dull testaceous ; the anterior femora are 

 for the most part fuscous, tinged with blue; the posterior femora are blue, except at the 

 extreme base and apex ; the coxae are bluish black ; the rest of the legs fuscous. The 

 sides of the head and pronotum are blue ; the rest of the head and thorax is black 

 tinged with blue. The scutellum and abdomen are coppery. 



