HOW INSECTS BREATHE. 143 



air attached to the underside of the abdomen. It is said, that 

 they project their club-shaped antennas into the air, and then, 

 jerking them back again, bring thus a little air, which they 

 then apply to the under surface of the thorax and abdomen. 

 This manoeuvre I have never been able to see ; the specimens, 

 the habits of which I have watched, used every now and then 

 to leave hold of the plant on which they were creeping, their 

 own lightness causing them to rise, and the air on their under 

 side turned them over in the ascent. They then crept along 

 the top of the water, back downwards, till they came to some 

 plant, by means of which they again descended. Some of the 

 larger species can swim, but not so easily or quickly as the 

 Dyticidce. This latter family will be referred to presently. 



The reason why we find some few aquatic Ilemiptera, 

 many Colcoptera, and none of any other order, is probably 

 connected with the state of the wings. It is evident that the 

 delicate state of the wings of a fly, bee or butterfly would be 

 much if not entirely spoiled by a long sojourn in water ; 

 those, on the contrary, of the Hemiptera being in great 

 measure, and of the Coleoptera entirely, protected by the 

 horny anterior wing or elytra, it is in these orders only that 

 we can expect to find any species with aquatic habits in 

 their perfect state. 



Considered in relation to the respiratory organs, however, 

 the most remarkable insect is Pteronarcys regalis, a Neurop- 

 terous insect from Canada. Among 150,000 species at present 

 known,* this alone possesses branchiae in its perfect state ! 

 Well therefore might Leon Dufour.the greatest Entomological 

 anatomist in the world, express unbounded astonishment at 

 this " extraordinary" and " illegal" fact, and doubt the 



* The lowest number estimated by Humboldt in his " Aspects of 

 Nature." 



