‘ 
on the Hphemeride. : 51 
tributed to the inner and terminal margins. It should 
be noted whether the longitudinal neuration is sparse 
and simple, or plentiful and complex: next, whether the 
eross-veinlets are scanty or numerous (especially in the 
costal and subcostal areas -before the nodi) : and then, 
whether the interneural veinlets of the terminal margin 
(if there be any of them) are derived from the longitu- 
dinal nervures, or from the cross-veinlets, or from the 
terminal margin only; and if they are only from the 
margin, it should be ascertained whether they are soli- 
tary or in pairs. Minute details of neuration are value- 
less ; only the general aspect or style of the neuration 
need be studied. 
In the hinder pairs of legs, the length of the tibie, as 
compared with the femora, should be noted; then the 
number of the tarsal joints, and the form of the wngues. 
If a fifth joint is present in the ¢arsus, its joining with 
the tibia may be obliterated, or indistinct, or clearly 
defined. 
As to the sexual peculiarities, it is important to examine 
first the oculi. Do the oculi of the male differ from those 
of the female in size only? or are they also divided into 
two parts? If they are divided, it must be ascertained 
whether the divisions are only ascalaphoid (as in Lepto- 
phlebia), or whether the upper part is elevated into a 
turbinate protuberance (as in Baetis). Next the forceps 
should be examined. Are the legs of the forceps sessile 
(as in Baetis) ? or are they inserted upon a lamellar ex- 
pictision of the penultimate segment (as in Siphlurus)? 
‘What are the relative proportions of their joints? It is 
lso very important to note whether the female has or 
jhas not a lamellar extension of the ventral margin of the 
‘apex of the penultimate segment.- Next the sete should 
be examined. Are their joints long, or short? Have 
‘they long or short pubescence towards their tips? Is 
the middle seta as long as the others in both sexes? or 
abbreviated in both, or rejected in both? Or is it re- 
jected by, or abbreviated in, the male only? Then it 
should be noted whether the anterior legs of the male 
have the femora unusually short, or not; and whether 
the anterior legs of the female are well developed or 
rudimentary. It should be ascertained also whether the 
eggs are extruded all at once, or not. 
25 
