HETEROPTERA. 317 



oars enables it to dart at the approach of danger, or in 

 the hope of prey, from the spot where it has long lain 

 motionless. 



This creature has a strong, thick, curved, sharp-pointed 

 and jointed beak, enclosing lancets, and will occasionally 

 wound the hand which captures it. What chance the 

 soft-bodied, plump little Tadpoles and sluggish thin- 

 skinned larvae of the water have against it may easily be 

 imagined, and a single Notonecta introduced into an 

 " aquarium " soon reduces almost any number of fat, 

 black Tadpoles to the same number of colourless, empty, 

 film-like skins. 



Under the delicately-tinted wing-cases of the Boatmen 

 are a pair of large, thin, milky-looking membranous 

 wings, which the insect uses freely on occasion. 



The larvae and pupae resemble the perfect insect, except 

 in the possession of wings, which, however, are indicated 

 in the pupae. 



The genus Noctonecta may be recognised by its three- 

 jointed tarsi and overlapping fore-wings. 



There are three species. 



A little creature one-sixth of an inch long, and much 

 resembling the Noctonecta, except in its greater width 

 in proportion to its length, and comparative shortness 

 of its hind-legs, is the little boat Ploa minutissima. 

 This is remarkable in the order as being an exception to 

 the rule of the fore-wings overlapping. They are united 

 down the back in a straight line. Like Notonecta Ploa, 

 the fore-tarsi are three-jointed. In Sigara and Corixa 

 they have but one joint. Corixa (in which genus are 

 ten species) may be recognised by the little shield or 

 scutellum being covered by the prothorax, and by an 

 approach in the nipper-like fore-legs to the character 



