FIELD BOOK OF INSECTS. 



laid singly in slits made by the females in underwater 

 plant stems. It is said that Acilius lets the eggs drop 

 upon the mud while swimming about and Colymbetes 

 arranges its eggs upon leaves. Miall remarks that many 

 a raw naturalist has put these beetles into his collecting- 

 bottle or aquarium, to find after a few hours that they 

 have destroyed or mutilated almost his whole live stock. 

 When the larva swims about in a leisurely way, the legs 

 are the chief means of propulsion, but it can also make a 

 sudden spring by throwing its body into serpentine curves. 

 It may also be seen to creep on submerged leaves, and to 

 cling to them when resting or lying in ambush. The tip 

 of the tail carries two small appendages. These, as well 

 as the last two segments of the abdomen, are fringed 

 with hairs, which no doubt increase the effect of a stroke 

 given to the water. But these appendages are chiefly 

 used to buoy up the tail, when the larva requires to breathe. 

 At length the larva ceases to feed, creeps into moist earth 

 near the edge of the water, makes a roundish cell there, 

 and changes to a pupa. 



The species of some genera, e. g. Bidesstis, are less than 

 .12 in. long. The following are among the largest species. 

 Colymbetes sculptilis: about .7 in. long; top of head black, 

 with two small, pale spots; pronotum, front of the head, 

 and margins of elytra, dull yellow; a black, transverse, 

 median bar on pronotum; elytra dark. The general 

 color of Dytiscus is greenish black. Dytiscus fasciventris: 

 length, an inch or slightly more; abdominal segments 

 reddish-brown with darker margins; pronotum margined 

 with yellow only on the sides, or with a faint trace of yellow 

 at base and apex ; each elytron of female with ten grooves, 

 which reach beyond the middle. D. liybridus: a trifle 

 more than an inch long; abdominal segments uniform 

 black; pronotum like fasciventris but shorter; yellow margin 

 of elytra of nearly equal width throughout, a narrow 

 yellow bar near apices; elytra of female smooth. D. 

 verticalis: length usually at least 1.4 in. ; abdominal segment 

 uniform black; pronotum margined with yellow only on 

 the sides; marginal yellow stripes on elytra narrowing 

 behind; narrow, oblique, yellow cross-bars, near apices, 

 often indistinct; elytra of females smooth. D. harrisii: 



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