112 Annals of the Carnegie Museum. 



Of the differences given above from H. inca those due to an in- 

 creased area of black might conceivably be the results of age, but no 

 such explanation will account for the wide dorsal yellow stripes of 3-5 

 or 6. 



I had first identified this male as H. cequatoriale, but neither the 

 description of that species, nor the male which is referred to it on page 

 107, give any indications of the lateral blackish line on segments 3-5 

 or 6 which separates the dorsal yellow from the ventral yellow of those 

 segments ; the tooth on the inner margin of the male of H. inca is 

 much less acute than in H. ce.quatoriale. Both of these differences 

 may be bridged over when a larger series of specimens is available. 



ii. Males with the inferior abdominal appendages undeveloped. 



39. Heteragrion triangulare Hagen. 



(Plate III, fig. 39.) 



Heteragrion triangulare Hagen, Bull. Acad. Roy. Belg. (2), XIV, p. 32, 1862; 

 Selys, Mem. Couron, Acad. Belg. xxxviii, p. 58, 1886. 



A complete male of this species has never been described, and de 

 Selys was uncertain whether the imperfect male which he referred 

 here in 1886 belonged to the species of 1862 or not. A description of 

 specimens which seem to be conspecific with the type female follows. 



d\ Pale reddish-brown with the following blackish markings : a 

 band on the labrum (leaving the free margin and a short streak on each 

 side pale ;^in the youngest male only a central round spot is blackish), 

 the nasus^most of the upper surface of the head from and including 

 the first antennal joint back to the posterior margin (leaving pale- 

 colored a stripe running from each lateral ocellus forward and outward 

 to the eye of the same side, and a shorter transverse isolated streak 

 each side a little posterior to the level of each lateral ocellus much 

 nearer to the^eye than to the ocellus), a narrow median perpendicu- 

 lar stripe on the anterior surface of the frons connecting the black of 

 the nasus with the black of the upper surface of the head, front lobe of 

 the prothorax (except for two minute dots), a band in the mid-dorsal 

 groove of the middle lobe confluent with a transversely elongated 

 elliptical spot'on the middle of the hind lobe, a mid-dorsal thoracic 

 stripe .4 mm. wide at mid-height, a mesepisternal stripe almost as wide 

 at its upper end as the sclerite but abruptly narrowed on its outer 

 (lateral) side [at nearly mid-height to half its former width (this 

 mesepisternal black stripe is completely separated from the black an- 



