450 On Aquatic Carmvorous Coleoptera or Dytiscide. 
D. 
534. Dytiscus lepidus, Oliv., Hydroporus lepidus, M.C.—Species pervariabilis. 
Ovalis, convexus, posterius acuminatus, nigricans, prothoracis lateribus testaceis, 
antennis pedibus elytrisque colore variabilibus, his semper picturatis ; prothorace 
versus latera striola indistincta; corpore subtus evidenter coriaceo, coxis posteriori- 
bus, sparsim subobsolete punctatis. Long. 3, lat. 1§ m.m. 
This is a most variable species, the elytra are sometimes largely black, with the 
lateral border and some very irregular waved marks yellowish; at other times 
they are yellow, with the suture, a large transverse patch on the middle, and a 
humeral dot black ; all variations occur between these extremes ; the punctuation 
varies very much, from a rather close but somewhat indistinct sculpture, to an 
obsolete one in which the elytra appear nearly smooth. Hydroporus rufulus, Aube, 
is founded on individuals in which the general colour is obscure reddish, the marks 
of the elytra being ill-defined. The smoother and paler forms occur only in the 
southern part of the area of distribution of the species. The sexes are scarcely 
distinguishable. 
Hydroporus optatus, Wehncke, is I consider a variety of this species. 
Western Europe and Northern Africa ; widely distributed but apparently wanting in Eastern Europe. 
Scotland, England, France, Spain, Portugal, Corsica. 320. 
535. Hydroporus formosus, Aube, M.C.—Oblongo-ovalis, conyexus, posterius 
acuminatus, crebre distincte punctatus, tenuiter pubescens, nigricans, antennis, 
pedibus, prothoracis lateribus elytrisque testaceis, his sutura, fasciis transversis 
undatis maculaque humerali nigris ; prothorace utrinque striola indistincta ; corpore 
subtus subopaco, minus distincte coriaceo, coxis posterioribus abdomineque basi 
utrinque fortiter punctatis. Long. 32, lat. 2 m.m. 
This species is extremely similar to some of the varieties of Dytiscus lepidus, 
but is a little more elongate and is readily distinguished by the coarse punctures 
of the under surface: a large series of specimens might possibly I think show it 
to be an extreme form of that variable species. The sexes appear to be scarcely 
distinguishable. 
Algeria, Tangiers, Tripoli. 321. 
536. Hydroporus escheri, Aube, M.C.—Oblongo-ovalis, convexus, sat nitidus, 
sat crebre et subtiliter punctatus, tenuissime pubescens, nigricans, antennis 
pedibusque testaceis, prothorace rufo, anterius et posterius nigricante, elytris 
maculis vel signaturis testaceis; thorace utrinque striola minutissima ; corpore 
subtus sat evidenter coriaceo, coxis posterioribus fortiter punctatis: abdomine 
seepius rufescente. Long. 32, lat. 2 m.m. 
