l^o 
THE STUDY OF INSECTS. 
Family N OTONECTIDiE (No-to-nec'ti-dae). 
The Back-swimmers . 
The Back-swimmers have the back shaped like the 
bottom of a boat, instead of flat like the true water-boatmen 
and they differ from all other aquatic bugs in that they 
always swim on their backs. 
The favorite attitude of the Back-swimmers is floating on 
the surface of the water, back downward, with the hind end 
of the body projecting sufficiently to admit of air being 
drawn into the space beneath the wings. When in this 
position their long oar-like hind legs are stretched outward 
and forward, ready for action. When disturbed they dart 
away toward the bottom of the pond, carrying a supply of 
air beneath their wings. Occasionally these insects will 
float on the surface of the water with their backs uppermost; 
and, like the water-boatmen, they can leap into the air from 
the water and take flight. 
The Back-swimmers feed upon insects and other small 
animals. In collecting them care must be 
taken or they will inflict painful stings with 
their sharp and powerful beaks. 
The greater number of our common spe¬ 
cies of this family belong to the genus Noto - 
necta (No-to-nec'ta) (Fig. 149). 
Fig. 149. — Notonecta 
undulata. 
Family NEPIDA (Nep'i-da^). 
The Water-scorpions . 
The Water-scorpions have two long bristles on the end 
of the body, which are grooved on the inner side. By put¬ 
ting these bristles together a long tube is formed, which the 
insects can project to the surface of the water, and thus ob¬ 
tain air for breathing, while resting on the bottom of the 
