1955] 
Gibbs — Females of Enallagma 
15 
of the anal appendages of the male. It has been almost 
impossible to divide the females into logical groups. Men- 
tion of the males of the species being compared, then, may 
make clearer the reason for comparing their females. 
Enallagma laterale would appear, from gross examina- 
tion of the male genitalia, to be close to E. piscinarium, 
E. davisi, and E. boreale, and perhaps to E. minusculum 
(Westfall, 1943). In these species the superior anal ap- 
pendage is shorter than segment 10 and ranges from 
bluntly rounded to deeply, but narrowly, cleft. E. minus- 
culum is most like davisi, but the lower arm of the superior 
anal appendage of the former appears prominently circular 
in lateral view. 
The male of E. recurvatum bears a superficial resem- 
blance to E. vernale, but the latter species is believed by 
Mrs. Gloyd (1943) and by Walker (1953) to be more 
closely related to cyathigerum. The recurved superior anal 
appendages of recurvatum are somewhat similar to those 
of E. hageni, which, however, are straight as viewed later- 
ally. Both laterale and davisi males are characterized by 
a lateral black mark on the eighth abdominal segment. 
Several recurvatum from Cape Cod also show this mark, 
although it is not commonly present. 
The caudal lamellae of the nymphs of E. ebrium and E. 
geminatum resemble those of laterale (Howe, 1921), in- 
dicating possible relationship. The nymph of recurvatum 
is unknown, and that of laterale has never been adequately 
described. 
The form of the mesostigmal laminae may prove to be 
indicative of relationships among the females of Enal- 
lagma. At any rate, the laminae are by far the best means 
for identifying the species. If Byers (1927) had pos- 
sessed females of both hageni and recurvatum, he could 
have recognized them both immediately by a glance at 
the laminae. In the key this character will play a prom- 
inent part. For illustrations of the mesostigmal laminae 
of most of the keyed species, I recommend the beautiful 
plates in Walker (1953). Those of laterale, recurvatum, 
and davisi (from the allotype) are figured in the present 
paper, along with that of minusculum. The latter is in- 
