318 INSECTS. 



to be noticed in the next family. In Sigara (containing 

 one species only) the scutellum is visible. 



All the Notonectidse swim well and quickly. 



The second family, Nepidse, contains the Water Scor- 

 pions, very different in appearance from the large-headed 

 boat-shaped Notonectidee, and are to be known by their 

 large prehensile fore-legs. 



There are three genera, each containing only one 

 species, and the reader will readily distinguish these. 



Nepa cinerea, the common Water Scorpion (PL XIII., 

 fig. 2), is a large, very flat, dingy, small-headed insect, 

 with a tail composed of two long bristles, and a scorpion- 

 like pair of fore-legs. It measures nearly an inch in 

 length, or, with the tail, one inch and a-half. It is a 

 slow and sluggish animal, living in the mud, and on the 

 water-plants in ponds, and, notwithstanding its sluggish- 

 ness, is a ravenous destroyer of other insects, especially 

 larvae. Probably its form and colours, resembling those 

 of a decayed leaf, conceal it from the notice of its prey, 

 and render swiftness in pursuit unnecessary. 



The eggs of the Water Scorpion are shaped like little 

 shuttlecocks, with feathers short and recurved. 



Naucoris cimicoides is nearly oval in outline, with a 

 much wider head than that of Nepa. The body is also 

 rather more convex, and indeed the insect may easily be 

 mistaken by a careless observer for a Water Beetle. It is 

 brown and shining, and swims with some activity. The 

 fore-legs (fig. 1 5, p. 38), are thicker, and even more cruel- 

 looking (when in sight) than the nippers of the Nepa ; 

 but they are not usually held extended. The Naucoris 

 has no tails.* 



* For an aquatic insect somewhat resembling this, but with simple 

 fore- legs, see Aphelocheirus in the next section. 



