DYTICID.E. — COLYxMBETES. 65 



The number and size of the spots on the elytra vary much. 



The chief distinctions of this insect from the foregoing consist in the more 



acuminated elytra, and the deeper colour; but I think it probable that both 



may eventually prove identical. 



More abundant than the last: common in ponds and ditches 

 round London; also in Norfolk. " Bottisham, common.' 1 — Rev* 

 L. Jenyns, 



Genus LXXXIV. — Colymbetes, Clairvilte. 



Palpi, external maxillary with the second and third joints equal, the fourth as 

 long as the two preceding united, with the apex obtuse: labrum minute, 

 rounded anteriorly: mandibles truncate, deeply emarginate at the apex: 

 mentum tridentate anteriorly. Antenna? slender, rather elongate ; the second 

 joint shortest, the third and fourth of nearly equal length : head subovate : 

 thorax short : elytra oblong-ovate : scutellum distinct : posterior legs natato- 

 rial : claws didactyle : tarsi five-jointed : four anterior tarsi of the males with 

 the three first joints nearly equally dilated. 



Colymbetes embraces an extensive series of insects, which differ 

 considerably m external form from each other; nevertheless their 

 general aspect is so extremely similar, and the gradations of shape so 

 close, that I shall not attempt to divide them into sections, but dis- 

 pose them in accordance with their apparent affinities, commencing, 

 agreeably to my usual practice, with those species which are nearest 

 allied to the foregoing genus, and terminating with such as approxi- 

 mate to the following. They are usually considerably larger than 

 any of the preceding insects of this family, and may be known by 

 possessing an exserted scutellum, compressed posterior natatorial 

 legs, elongated tibiae, didactyle claws, and an obtuse terminal joint 

 to the external maxillary palpi. 



Sp. 1. oblongus. Plate XII. f. 1. Ohlongo-ovatus , ferrugineus, subtilissime 

 punctulatus, occipite,pectore ventreque nigris, elytrisfuscis, pallido margin atis, 

 (Long. corp. 3| — 4 lin.) 



Dy. oblongus. Illiger. — Co. oblongus. Steph. Catal. p. 48. No. 479. 



Oblong-ovate, ferruginous, finely punctulate: vertex more or less dusky : thorax 

 with the disc blackish, the margins ferruginous, above rather convex, very 

 delicately punctulate-strigose : elytra oblong-ovate, attenuated towards the 

 apex, a little convex, finely and closely punctulate, with several striae of irre- 

 gularly-placed deeper impressions, dusky-ferruginous, the basal and lateral 

 margins paler: breast and abdomen beneath dark pitchy-black; the margins 

 of the segments paler : legs and antenna? pale-ferruginous. 



Var. 0. With the vertex and thorax immaculate-ferruginous. 



Mandibulata. Vol. II. 1st Sept. 1828, f 



