INSECTA MADERENSIA. 83 



A largo and beautiful Colymbetes, and apparently peculiar to Madeira, — having 

 been first described by Pabricius, from a specimen in the Banksian collection, in 

 the year 1792. It is universally distributed, beyond the elevation of about 1000 

 feet, but is more especially abundant between the limits of from 3000 to 4000, 

 above the sea. Owing to the rapidity of the mountain torrents, water insects are 

 comparatively scarce in Madeira ; and the pi'esent species would seem to be one of 

 the few which is able to exist indiscriminately, its powerful and greatly developed 

 wings enabling it to take refuge in the most isolated pools, and in other spots 

 which it could not possibly reach except by flight. In the streams which issue from 

 the Paul da Serra it is common ; and I have observed it, likewise, in most of the 

 rivers flowing towards the south of the island, particularly in the Ribeiro de Santa 

 Luzia and at the Curral das Romeiras, — where it occurs in profusion at nearly all 

 seasons of the year, though especially dui'ing the autumnal months. 



Genus 26. AGABUS. 



Leach, Zool. Miscall, iii, 69, 72 (1817), 



Corpus fere ut in genere prsecedenti, sed minus. Palpi labiates articulis secundo et ultimo subsequali- 

 bus : mentuin antice dente medio brevi subemarginato instructum : et unguiculi postici (ut 

 anteriores) aequales curvati mobiles. 



Agabus may be readily distinguished from Colymbetes proper by the smaller 

 size of the species which compose it, by the second and thii'd joints of its labial 

 palpi being of almost the same length, and by its two hinder claws being, like the 

 remainder, equal and moveable, — instead of unequal and with the larger one fixed. 

 So far as I have hitherto observed, the genus has three representatives in Madeii-a ; 

 one of which, moreover, is peculiar to the island, 



65. Agabus bipustulatus. 



A. oblongus subdepressus subseneacenti-nigropiceus, minutissime longitudinaliter strigulosus, ore et 



capitis maculis duabus obscurissimis in fronte sitis ferrugineis, elytro singulo longitudinaliter 



confuse triseriato-punctato, antennis pedibusque picescenti-ferrugineis. 



Variat colore plus minusve picescenti, — prsesertim in foemina, cujus superficies plerumque opacior 

 est. 



Long. Corp. lin. 5-5i. 



Dytiseus bipustulatus, Linn. Si/st. Nat, ii. 667 (1767). 



_, Fab, Syst. Eleu. i. 263 (1801). 



Cohjmletes hipusttclatus, Steph, III. Brit. Ent. n. 80 (1829). 

 Agabus bipustulatus, Aube, Hydrocan. 357 (1838). 



Habitat in rivTolis Maderse, necnon in aquis quietis ; ubique vulgaris, sed supra 1000' s, m. prsedominans. 



A. oblong, and somewhat depressed, dark piceous-black, and with a shghtly seneous tinge ; the entire 



m2 



