LEPTOHYPHES.—BAETIS. 13 
subimago, and indicate the possession of a notal hood by the advanced nymph. Their 
homologues, present in the subimago of Hphemerella notata, are not retained by the 
imago. The wings of Leptohyphes are fringed, and the ventral lobe of the ninth abdo- 
minal segment is well developed, with the extreme tip subacute and deflected upwards. 
BAETIS. 
Baétis, Leach, Brewst. Edin. Encycel. ix. 137 (1815); Eaton, Rev. Mon. Ephem. p. 156, tt. 16, 17. 
figg. 29 a—f (adult details), and t. 44 (nymph) (1884-5). 
Species of this genus are numerous in most parts of the world. Many of them 
are distinguished by characters which cannot be observed in dried specimens (such as 
the form of the male genitalia), and are devoid of any other particularly distinctive 
characteristics sufficient to mark them off each from its nearest allies. Descriptions 
made from the dried insect are of little practical use in such cases, where even actual 
comparison of specimens hardly yields anything whereby identification of species can 
be decided. 
1. Baetis salvini. 
Baétis salvini, Eaton, Rev. Mon. Ephem. p. 170, t. 16. fig. 29 @ (adult ¢ details) (1885) °. 
Hab. Guaremaia, Zapote (one 2 imag.), Cerro Zunil (one ¢ subimag.), and Panima 
in Vera Paz (one 3 and two 2 imag.) (Champion); Costa Rica, Volcan de Irazu 
6000 to 7000 feet (Rogers!; subimag., ¢ imag.). 
The subimago from Cerro Zunil has light sepia-brown wings with pitch-brown neura- 
tion, and the condensation of colouring along the margins of the nervures and cross- 
veinlets is noticeable only in a very small part a little beyond the middle of the wing. 
The difference between it and the specimen from the Volcan de Irazu described in the 
Rev. Mon. Ephem.! may perhaps be due to its being less advanced towards moulting. 
The ¢ imago from Panima has the femoral markings rather lighter, and the 
markings of the sete not in exact accordance with those of specimens from Irazu 
described in 1885. The coloration of the body is well preserved, which was not 
the case in the specimens referred to. Thorax light pitch-brown or raw umber 
above, varied with light ochreous yellow; metanotum pitch-brown. Dorsum of 
abdomen of a rich pitch-brown, with oblique lateral markings that are concolorous 
with the light ochreous or flavescent venter, and leave a broad serrate lateral 
stripe of the darker colour along the pleura and extreme edge of the venter. The 
lighter markings are in segments 2-8 an oblique longitudinal stripe on each side 
of the back, broad in segments 3-5, and successively narrower in segments 6-8; 
the stripe is faintly indicated in the ninth segment, which has in addition a tri- 
angular spot of the same colour at the apical margin just above the pleura. The 
tenth dorsal segment, likewise largely of that colour, has a median ovate very light 
