TRACHEA TA 363 



Sub-order 1. Heteroptera. 



Chaeacteristics. — The Heteroptera haw the proximal half of 



their anterior wirujs horny, the distal half membranoiis ; 



they lie flat, overlapping OTie another. Many are apterous. 



The prothorax is large and free. The proboscis arises from 



the front part of the head, and when at rest lies against the 



thorax. 



A few families may be mentioned : 



Family Notonectidae (water -boatmen). — These insects 

 always swim on their back, which is convex, Kke the bottom 

 of a boat, whilst the ventral surface is flattened. The legs 

 are long, especially the posterior pair, which are flattened for 

 swimming. They fly well, but can scarcely walk ; when dis- 

 turbed they dive beneath the surface, carrying a supply of air 

 for respiration beneath their wings. They remain for some 

 time under water, holding on to aquatic plants, etc. 



Family Nepidae (water-scorpions). — The members of this 

 family are provided with a pair of long tracheal tubes at the 

 end of their abdomen. Their body is flat and oval {Nepa), or 

 elongated and linear {Banatra) ; their fore limbs are raptorial, 

 their hind limbs adapted for swimming. They are carnivorous, 

 living chiefly on the larvae of aquatic insects and young fish. 

 Their eggs are laid in the water, on stems of plants or under 

 stones. 



Family Hydeobatidae. — Aquatic insects of oval or elon- 

 gated form, which run rapidly on the water's surface, and are 

 usually found in colonies. The antennae are four-jointed and 

 unusually long. There are often two adult forms found at 

 the same time — one kind being winged, the other wingless. 

 This family includes the Halolates, a marine insect found 

 swimming on the surface of the sea in the tropics. It feeds 

 on dead animals which float on the surface, and is said to 

 attach its eggs to the Sargassum sea-weed. 



Family Eeduviidae. — A very large and diverse family, 

 including many insects of brilliant colour and some of con- 

 siderable size. The proboscis is short and three-jointed. They 

 are predaceous, and live for the most part on the blood of 



