324 INSECTA. 



Hygrobia, Lat. — Hydrachna, Fab. Clairv. — Pcelobius, Schoenh. 



The tarsi also composed of five distinct joints, the four anterior 

 of which are almost equally dilated at base, in the males, into a little 

 palette forming a long square; but the antennae are shorter than the- 

 head and thorax; the body is ovoid and very thick in the middle; 

 eyes prominent(l). 



Hydroporus, Clairv. — Hypliydrus, Schoenh. 



The four anterior tarsi nearly similar, and spongy underneath, in 

 both sexes, composed of but four distinct joints, the fifth being de- 

 ficient or very small and concealed, as well as a part of the last, in a 

 deep cleft in the third. 



These Insects have no apparent scutellum(2). 



We might separate from them some species(3) in which the body 

 is almost globular, and where the last joint of the four anterior tarsi 

 is very small and projects but little beyond the preceding one — Hi/' 

 phydrus, Lat. — The body of the rest is oval, and not so thick(4). 



Sometimes the antennae are slightly dilated and wider in the mid- 

 dle of their length; the last joint of the labial palpi is emarginate, 

 and appears forked. 



Add for the American species of Colymbetes the C. erythropterus, fenesiralis, 

 amhiguiis, seriatns, nitidus, bicarinatus, venustus, glyphicus, obtusatus, &c. Of tlie 

 G. Lacophilus we have the L. maculosus and proximus. Jim. Ed. 



(1) Hydrachna Hermanni, Fab.; Lat. Gener. Crust, et Insect., I, vi, 5; Clairv., 

 Entom. Helv. II, xxvii. A, a; — H. uUginosa, Clairv., lb. B, b. 



Tiiese Insects with the Ilalipli, in the system of Leach — Zool. Mlscell. p. 68 — 

 form a particular group, the characters of which are: a scutellum; all the legs 

 adapted for walking, with five joints to all the tarsi and two terminal hooks to the 

 last. 



The Hygrobiae have their exterior palpi somewhat enlarged at the end; two 

 stout and approximated spurs at the extremity of the tibiae, and their anterior tarsi 

 susceptible of being doubled under the tibiae to which they are annexed. 



(2) In the preceding divisions, some small species excepted, it is very apparent. 

 Add of American species the Hydrop. undulatus, oppositus, niger, catascopium, 



lacustris, paralklus, undulatus, he. Jim. Ed. 



(3) The Hyd. gibba, ovalis, scripta. Fab.; Hyphydrus lyratus, Schoenh., Synon. 

 Insect., II, iv, 1. 



(4) The Dytisci inxqualis, reticulatus, confluens, picipes, pidus, gemtnus, linea- 

 tusyhalensis, duodecim-piustulatus, dmsalis, sexpustulatus, palustris, depressus, litu- 

 ratus, planus, erythrocephalus, nigrita, granulans, Fab. See Schccnherr, Synon. 

 Insect. II, genus Hyphydrus; — Panz., Index Entom., genus Hydroporus,- — and 

 Clairv., Entom- Helv. II, the same genus. 



