356 AN INTRODUCTION TO ENTOMOLOGY 



place a great expansion of the wings, the change at this time being 

 much greater than at either of the previous molts. There are many- 

 forms in this order in which wings are not developed. In some 

 species all individuals are wingless; in others there are two forms of 

 adults, the winged and the wingless. 



In this order we find variations in structure which correspond 

 closely with variations in habits. There are certain families the 

 members of which are truly aquatic, living within the water, through 

 which they swim and to the surface of which they come occasionally 

 for air. There are others which are truly terrestrial, living upon the 

 surface of plants, or in other positions away from water. There are 

 still other families the members of which hold an intermediate position 

 between the aquatic and the terrestrial forms, living upon the surface 

 of water or in marshy places. 



In the systematic arrangement of the families of the Hemiptera 

 adopted here the aquatic forms are placed first ; the terrestrial forms, 

 last; and the semiaquatic forms hold an intermediate position. The 

 sequence of the families is more fully indicated in the following 

 synopsis. 



SYNOPSIS OF FAMILIES 



The Short-horned Bugs. Bugs with short antennae, which are nearly or quite 

 concealed beneath the head. 

 Bugs that live within water. 



The Water- boatmen, Family CoRixiD^. p. 360. 

 The Back-swimmers, Family Notonectid^. p. 362. 

 The Water-scorpions, Family Nepid^. p. 364. 

 The Giant Water-bugs, Family Belostomatid^. p. 365. 

 The Creeping Water-bugs, Family Naucorid^. p. 367. 

 Bugs that live near water. 



The Toad-shaped Bugs, Family Gelastocorid^. p. 368. 

 The Ochterids, Family Ochterid^. p. 368. 

 The Long-horned Bugs. Bugs with antennas at least as long as the head, and 



prominent except in the Phymatidae, where they are concealed under the 



sides of the prothorax. 

 The Semi-aquatic Bugs 



The Shore-bugs, Family Saldid^. p. 369. 



The Broad-shouldered Water-striders, Family Velhd^. p. 369. 

 The Water-striders, Family Gerrid^. p. 370. 

 The Mesoveliids, Family Mesovelhd^. p. 372. 

 The Hebrids, Family Hebrid^. p. 372. 

 The Water-measurers, Family Hydrometrid^. p. 373. 

 The Land-bugs. 



The Land-bugs with four-jointed antennce. 



The Schizopterids, Family Schizopterid^e. p. 373. 



The Dipsocorids, Family Dipsocorid^. p. 374. 



The Isometopids, Family Isometopid^. p. 374. 



The Leaf-bugs, Family MiRiD^. p. 375. 



The Termatophylids, Family Termatophylid^. p. 377. 



The Flower-bugs, Family Anthocorid^. p. 377. 



The Bedbugs, Family Cimicid^. p. 378. 



The Many- combed Bugs, Family Polyctenid^. p. 379. 



The Nabids, Family Nabid.«. p. 380. 



The Assassin-bugs, Family Reduviid^. p. 380. 



The Ambush-bugs, Family Phymatid^. p. 382. 



The Unique-headed Bugs, Family Enicocephalid^. p. 383. 



