62 Rev. A. H. Haton’s Monograph 
Palpi maxillares tri-articulati ; inferiores ultimis articu- 
lorum late expansis. Mandibulee antice longe prolongatz, 
per-robustz, extrinsecus serrate. Frons bicornuta, cor- 
nibus dentatis, dentibusque lateralibus. Labrum subro- 
tundatum, apice acuto. ‘Tibize antice intus dentate. 
(Corn.) 
Inter ultimam metamorphosem exuyias alarum mas 
seepe evertit; feminz tamen subimago seepissime status 
adultus est, pelle retenta. (Swam.) 
Imago. Oculi integri. Setarum media est brevissima. 
Alze quatuor. Tarsi postici quadri-articulati. Ovival- 
vula femina caret. Forcipis pedes pedicillati, quadri- vel 
forsan quinque-articulati, proximis articulorum longissi- 
mis. 
The nymphs live in burrows which they excavate a little 
below the water-mark, in the clayey banks of large and 
tranquil rivers. 
Palingenia longicauda. 
(Genitalia maris, Pl. III. fig. 17, 17a.) 
Hemerobius, Clut. 1634. Hphemera longicauda, O1. 1791. 
H. fuliginosa, Georgi, 1802. LH. flosaque, Illig. 1802. 
Senblis marginata, Pz. 1804. H. Swammerdiana, Lat. 
1805; H. Swammerdamiana, Shaw, 1806. 
Pedes postici bi-unguiculati. 
Imago, v.s.s. d. Alee cervine, nervis luridis. ‘Tho- 
rax luteus; prothorax longitudinaliter quinque-striatus,” 
(Pict.). Tarsorum posticorum primus, secundus et 
tertius articulorum subzquales, quarto paulo breviores. 
Ungues tenues conformes. Abdomen supra saturate um- 
brinum. Pedes, venter, setaque, pallide lurido-ochracei. 
Long. corp. ¢ 23, al. 24, set. 70 mm. (Pict.) 
Hab.—The large rivers of Central Europe (e.g. in Ger- 
many, Hungary, Austria, and the Netherlands); also in 
the Caucasus. About Midsummer. 
Swammerdam’s supposition, that the aquatic stages of 
development occupy three years, seems merely a gratuitous 
surmise ; for he reared no specimens, and founded his 
conjecture upon the differences of size presented by the 
nymphs alone. But though in this instance Swammer- 
dam was inaccurate, his famous treatise will remain a 
monument of his perseverance, and his extraordinary 
powers of research. 
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