NEUROPTERA. — EPHEMERID. 33 
abdominal segments are ‘of equal size) has formed the subject of a 
valuable paper upon the circulation of the blood, by Mr. Bowerbank. 
(Ent. Mag. vol. i. p. 239.) 
The larvee and pup figured by Rosel (Jns. Belusé. tom. ii. tab. 12. 
f. 3,4.) seem, at least so far as they can be determined from the 
figures, to be similarly constructed to the pupa figured by Goring and 
Pritchard; the head being of moderate size, and the anal filaments 
deeply fringed; but the imago (fig. 6.) is represented as possessing 
four wings and two tails: so that either the genus Baetis, as even now 
restricted, must comprise several distinct types, or Rosel must have 
erred in giving four wings to his imago. 
The species which afforded Swammerdam materials for his admi- 
rable history of the Ephemera, abounds to an astonishing extent in 
the rivers of Holland and Germany, and makes its appearance regu- 
larly, in swarms, at the mouths of the Rhine, Meuse, Wael, Leck, and 
Ysel, during three succeeding days, about the feast of Olophius and 
St. John. It is considerably larger than E. vulgata, with four wings 
and two long hairy tails; and has been named E. Swammerdiana by 
Latreille, in honour of its historian. It clearly belongs, however, to a 
distinct genus ; its larva burrowing in the ground, with short broad 
legs, and its head cornuted (see tab. xiv.): the first abdominal seg- 
ment is not furnished with gills, but each of the six succeeding seg- 
ments has a pair on each side; the posterior in each pair being very 
small, and termed by Swammerdam rowing fins. The male pupa 
differs from the female in the larger size of the head, and especially 
of the eyes. 
Reaumur (Mémoires, tom. vi. Mém. xii. tab. 42—44.) has given 
numerous details of a large species, which in several material respects 
differs from any of the foregoing; it has four wings, and three tails, 
which in the female are of equal length, but in the male the central 
one is not half the length of the abdomen: the abdomen of the male 
is armed at its extremity beneath with a pair of straight appendages 
of considerable length, in addition to the pair of articulated forceps ; 
the meso- and meta-thoracic spiracles are of large size; the female 
deposits her eggs in two long oval masses. The larva burrows in 
ground at the sides of the rivers, and has short broad legs, the man- 
dibles are greatly elongated, curved, and armed along the under surface 
with two rows of small points, and an apparently articulated hook at 
the tip; and the gills are of an elongated kidney shape, narrowed 
VOL. II. D 
