INSECTS OF NEW BRUNSWICK. 5 



the vein, and this number we find in Oligoneuria and, perhaps, in Lachlania. The 

 portion of the area of this vein covered by the upper branch and its forks is almost 

 always greater, generally considerably greater, than that covered by the lower branch ; 

 an exception to this will be found in Polymitarcys where the lower area is greater, 

 owing to unusual breadth of wing combined with narrowness of the area covered by 

 the intermedian vein, which has been crowded out of much of its natural ground by 

 this lower bi-anch. Some of the allies of Polymitarcys, especially 'Asthenopus and 

 Pentagenia, also have this area of the lower branch larger than usual, although not 

 larger than that of the upper branch, and some other genera not placed near it exhibit 

 a simOar propensity ; but as a general thing, the area covered by the lower is scarcely 

 more than half as large as that covered by the upper bi-anch, and not infrequently it is 

 less than one third its extent. The upper branch usually forks close to the base, 

 occasionally at the very base, and sometimes the upper of the forks is amalgamated 

 at the base with the scapular vein, as in Asthenopus, Tricorythus and Chloeon, and 

 to a certain extent in Coenis, so as to give it the appearance of originating from that 

 vein, and of complete independence of the externomedian ; whether thus severed from its 

 connections, or plainly arising from the externomedian root, this upper fork of the upper 

 branch runs in proximity to the scapular vein, parallel or subparallel to it, and, excepting 

 where the venation is occasionally simple (as in Oligoneuria, &c.), always emits from its 

 lower surface in the central portion of the wing one, two, or three nervules ; the first 

 and second of these nervules are usually pretty near together at base, but all generally 

 reach the border at unequal distances apart, the inequality being made good by 

 intercalary longitudinal nervules ; these intercalary nervules often curve at their inner 

 extremities toward or to one or another of the adjoining nervules, assuming then the 

 appearance of regular branches, while the nervules proper ai-e themselves oftener 

 detached from their base ; so that it is sometimes difficult to tell whether a given vein 

 should be considered normal or intercalary. The lower fork of the upper branch is 

 occasionally simple, as in the Tricorythus, but usually forks once at about the middle 

 of its course, rarely near the base, and very frequently encloses an intercalary nervule 

 between these branches, but no intercalary nervules (excepting such as often break 

 up the extreme margin into an irregular meshwork of veins) ever intervene between the 

 upper nervide of this fork and the lower nervule of the upper fork, nor between its 

 lower nervule and the upper nervule of the lower bi-anch of the externomedian vein, 

 excepting in the rare instances where this lower nervule is detached from its base, and 

 takes on the form of an intercalary nervule. 



This lower branch, as has been said, is usually forked to a less extent than the upper 

 branch, but a conspicuous exception is found in Polymitarcys where the brancli is made up 

 of a large number of sub-convergent sinq^le rays, directed from the outer margin 

 toward various parts of the upper internomedian nervule, but generally lost before reaching 

 it. In general, however, its area is only about half that of the upper branch ; it usually 

 forks close to the base, and each or either of its branches may again subdivide once ; all other 

 nervules in the area are sure to be intercalary ; where it forks only once there is usually 

 a single intercalary nervure midway between the branches, which seems to belong to one 

 or the other of them and to represent its fork ; while between it and either branch there 



