560 Mr. Kenneth J. Morton on 
NEMOURA. 
(Nervures of pterostigma forming a y.) 
No caudal sete. Labial palpi short and approximate. Tarsi 
with 2nd joint short, Ist and 3rd long. Wings in rest ordinarily 
flat. 
Albarda has shown that the above-mentioned character 
in the neuration of Tniopteryx is not absolutely charac- 
teristic, as his 7’. neglecta* has the wings in the normal 
condition of a Nemoura. ‘The condition of the tarsi will 
at once prevent any confusion between these two genera, 
and the wing-neuration character seems to hold guod as 
a means of separating Nemoura and Lewuctra, which 
agree with each other as regards the tarsi. 
With regard to the position of the wings in rest, 
there appear to be in Nemowra slight deviations in the 
direction of the position they occupy in Leuctra ; this 
has been noticed in N. Meyert when alive. Other 
characters made use of in the above diagnoses will also 
require further investigation ; for example, the presence 
or absence of caudal sete. Seta probably exist in at 
least one of the species here described as a Nemoura. 
Then the appendages of various species here retained 
under Nemoura show so much diversity of structure that 
it is almost certain that, sooner or later, further generic 
subdivision will take place based on these parts. 
The figures are from drawings made under the micro- 
scope with the camera lucida. In most cases, two views 
are given—one from the side, the other from beneath— 
the object beimg held slightly in front of the observer. 
These figures and the descriptions were all made from dry 
examples for the sake of uniformity. These insects are 
subject to great variations in size and colour, according 
to locality, and they have almost all a tendency to 
become blackish or unicolorous when dry, and colour 
characters are, therefore, not of great importance, except 
in a broad way. 
Another feature in these insects (and in all Perlidz) 
is the instability of neuration, and few details under this 
head are sufficiently constant to be of help in the 
separation of species. It has been the practice to lay 
* “ Annales de la Soc. Ent. de Belgique,” Tome xxxiil. 
