420 SYNOPTIC COLLECTION. 



mouth parts is the possession of palpi, and the discovery 

 of these organs by Leon l tends to confirm his statement 

 that there is a complete homology between the Hemipter- 

 ous mouth organs and those of biting insects. 



The Hemiptera are divided into two groups, the Het- 

 eroptera and the Homoptera. The Heteroptera are the 

 more generalized, inasmuch as they have more direct 

 development than the Homoptera, and the thoracic and 

 abdominal regions are more like those of larval cock- 

 roaches. 



The larvae and adults of some of the water-inhabiting 

 Hemiptera bear a greater resemblance to the Thysanura 

 in the general proportions of the body than do the terres- 

 trial forms like the typical Anasa or squash-bug. For 

 this reason they will be considered first. 



The generalized characters of Notonecta are seen in 

 the larva. Besides these both the larva and the adult 

 (No. 1038) possess adaptive features fitting them for 

 aquatic life. The back is shaped somewhat like the bot- 

 tom of a boat and the insect swims with it downward 

 hence the name of back- swimmer. The hind pair of legs 

 have become efficient oars ; concomitantly their structure 

 has changed and they have become long, flattened organs 

 fringed with hairs. 



The water-inhabiting Hemiptera, like all water insects, 

 breathe air. Notonecta often comes to the surface and 

 stows away a supply under its wings, while another water 

 boatman, Corixa (No. 1039), is enveloped in a film of -air 

 which gives it a silvery appearance. 



The largest Hemipterous insect is the giant water-bug, 

 Belostoma americanum (No. 1040, dorsal and ventral 

 side), which on account of its size is particularly helpful 

 to the student. 



The segments of the thorax in this insect are free like 

 those of the abdomen. The head is flat and placed hori- 



1 Zool. Anz., XX, 1897, p. 73. 



