HYDRADEPHAGA. 6l 



species, strongly toothed in the middle ; the ligula 

 horny, quadrate, with the paraglossse soldered to its 

 sides ; the palpi are mostly thread-like ; the maxillae are 

 fringed on the inner side ; the scutellum is either very 

 small, or not visible : the basal joints of the front tarsi 

 are widened in the males, and all the species have stout 

 and large wings. 



Their larvse are also aquatic, and very predaceous ; 

 they are mostly elongate, somewhat cylindrical, and 

 tapering to the tail, and with a broad head armed with 

 two strong, pointed jaws. They generally construct 

 hollow cells in banks of ponds, etc., and turn into pupse 

 underground, near their native element. 



Our species may be divided into two families, the 

 Dytiscidae and Gyrinida ; in the former of which the 

 antennse are either thread-like or straight, and in the 

 latter broad, short, and elbowed. 



1. The DYTISCID^E are separated into four sub- 

 families, the Haliplides, Pelobiides, Hydroporides, and 

 Dytiscides. 



Of these, the HALIPLIDES form a good connecting link 

 with the Bembidiides in the Geodephaga, their legs not 

 being widened, and formed for swimming, as in the othei 

 Hydradephaga, but thin, slender, and adapted for walk- 

 ing; indeed, the species though of aquatic habits swim 

 but feebly, frequenting weeds, etc., and running readily, 

 with an alternate motion of the legs. The basal joints 

 of their front tarsi, also, are not dilated in the males, 

 a character found in some of the Bembidiides, and very 

 rare in the Hydradephaga, some members, of which 

 afford, perhaps, the greatest known development of this 

 structure. Their head is not so sunk in the thorax as 

 in the majority of their allies - } and, lastly, in the genus 



