ADEPHAGA HALIPLIDAE 



209 



there is a file on the inside of the wing-cases, and the Insect 

 turns up the tip of the abdomen and scrapes the file therewith. 

 The Insects are called squeakers in the Covent Garden market, 

 where they are sold. 



Fam. 8. Haliplidae. — Antennae hare, ten-jointed ; meta- 

 stermim marked ly a transverse line; posterior coxae prolonged 

 as plates, covering a large 

 part of the lower surface 

 of the abdomen ; the 

 slender, hut cluhhed, hind 

 femora move between these 

 plates and the abdomen. 

 The Haliplidae are 

 aquatic, and are all small, 

 not exceeding four or five 

 millimetres in length. 

 The ventral plates are 

 peculiar to the Insects of 

 this family, but their func- 

 tion is not known. The 

 larvae are remarkable on 

 account of the fleshy pro- 

 cesses disposed on their 

 bodies ; but they exhibit 

 considerable variety in 

 this respect ; their man- 

 dibles are grooved so that 

 they suck their prey. In 

 the larva of Haliplus, 

 according to Schiodte, 

 there are eight pairs of 

 abdominal spiracles, but 

 in Cnemidotiis (Fig. 95, 

 B), there are no spiracles, 

 and air is obtained by 

 means of a trachea traversing each of the long filaments. The 

 Insects of these two genera are so similar in the imaginal instar 

 that it is well worthy of note that their larvae should be distin- 

 guished by such important characters. Haliplidae is a small 

 family consisting of three genera, having about 100 species ; 

 VOL. VI p 



Fig. 95. — Cnemidohts caesus. England. A, Imago ; 

 B, larva, highly magnified. {After Schiodte. ) 



