38 



MANDIBULATA. — COLEOPTERA. 



shanks and tarsi fringed with hairs ; the first segment is largest, 

 and armed above and below with a scaly plate : these larvse subsist 

 chiefly upon those of the Libellulidse, Agrionidse, Ephemeridse, 

 Culicidse, and Tipulidse, which they seize and retain with their 

 powerful jaws, and extract their juices through their perforated 

 extremities : they swim with facility by means of the ciliated legs ; 

 and, like the imago, are compelled to approach the surface of the 

 water occasionally to respire, where they suspend themselves by 

 means of the caudal appendages, leaving the tip of the cylindrical 

 tubes exposed to the atmosphere ; when ready to undergo their 

 change, they seek for a convenient spot in the neighbouring banks, 

 and form an oval cavity, in which they become pupse, and remain 

 in that state from fifteen to twenty days, when the imago is pro- 

 duced: the latter chiefly occurs from April to August. 



The indigenous genera which have come beneath my observation 

 may be thus discriminated from each other : 



["4-antici 4-avti- 

 I culati: Ungues 



( nullum: | 

 Tarsi \ 



omnes 5-articu- 

 lati: Pedes 



C omnes di- 



dactyli : 

 Pedes 



C postici monodactyli : 



C.. omnes didac- f subglobosum : 

 tyli: Cordis! 



(_ depressum : 

 f natatorii : I in medio dilatatee : 

 j Antennae < 

 j (^ simplices : 



gressorii : 



79. Hyphidrus. 



80. Hvgrotus. 



81. Hydroporus. 



82. Noterus. 



83.Laccophilus. 

 77- Haliplus. 



gressorii: 78. P^elobius. 



-distinc- 

 tum: 

 Ungues -[ 



natatorii : Palpi 

 rnaxillares ex- 

 tend articulis J 



2et3 



fsequalibus, fobtuso: 84. Colymbetes. 

 4-to apiceK subulato : 85. Agabus. 

 (_ oblique^ 

 subtrun- 

 cato: 87- Dyticus. 



(^postici monodactyli : 



(Jnsequalibus, | S " at ^ 

 4-fo apice j ^ 



V. dato: 



86. Hydaticus. 



89. Actlius. 

 88. Cybister. 



Genus LXXVII. — Haliplus, Latreille. 



Palpi, external maxillary, and labial, with the terminal joint minute, subulated, 

 the preceding elongate, clavate; the first and second very short: labrum 

 emarginate anteriorly : mandibles short, triangular, internally excised at the 

 apex: mentum transverse, anteriorly tridentate, the central tooth shortest. 

 Antennae linear, apparently 10-jointed, the basal joint minute, the fourth 

 shortest, the terminal elongate, acute : head ovate, exserted : eyes moderately 

 prominent : thorax with its base triangulate, the central angle occupying the 



