

304 THE NORTHERN MICROSCOPIST. 
HEPTAGENIA LONGICAUDA. 
(Family-Ephemeride.) 
By W. BLAcKBURN, F.R.MLS. 
? the Northern Microscopist for September last, some aquatic 
forms of the genus Heptagenia are mentioned as having been 
found at Bramhall during a ramble of the members of the Man- 
chester Microscopical Society in that neighbourhood. Being 
desirous of ascertaining the species to which they belonged, I 
reared some specimens collected on that occasion through the sub- 
imago into the imago state, and then found them to be Heptagenia 
longicauda (Eaton). Stephens has described this species under two 
different names, Baetis longicauda and B. subfusca. It appears to 
be peculiar to the British Isles, although the genus to which it 
belongs is one of the most widely distributed throughout Europe 
and America. The eight species found in Great Britain are //. 
semicolorata, volitans, flavipennis, elegans, venosa, longicauda, in- 
signis, and lateralis. 
The Rev. A. E. Eaton in his valuable monograph describes 
the nymph of this genus as “ Nympha agile reptans, laminis 
branchialibus utrinque septem; laminz simplices integra, fasci- 
culis e radicibus singulis filamentorum branchialium.” Herein 
is an important omission, for bundles of branchial filaments 
which are attached to the roots of the first six pairs of plates, 
forming the external abdominal gills, are in fact absent from 
the seventh pair. Westwood, in his description of the aquatic 
form of Baetis of De Geer, which is the same genus, notices this 
peculiarity of the nymph. Some other characteristics of the nymph 
are a very broad head and thorax, comparatively short antenna, 
maxillary palpi two-jointed, and the legs with the femora widely 
compressed. Altogether the insect has an appearance of stoutness 
and strength, when in the water, differing most materially from the 
slender and graceful form it assumes when it casts off its swaddling 
clothes and emerges as a subimago. In the latter condition it 
assumes the characteristic attitude of the genus when at rest, with 
all its feet on the ground, the wings erect, and the two caudal setz 
divergent, the central filament of the tail having been left in the 
water. It has four wings, but they appear to be unnaturally small 
and wanting transparency, owing to their being folded up in the 
cases of the subimaginal skin. It now waits in quietude for this 
skin to dry, and then endeavours to extricate itself, and, escaping 
through an opening in the thorax, appears in its final form of an 
imago. In a few minutes the wings expand to their full dimensions, 
and appear of a more glassy nature, with the nervures more clearly 

