INSECTS. 



125 



each side of the thorax, and emit a vivid light visible even 

 in broad daylight. 



NOTE. The light of the common fire-fly (Lamfyris) gives a spec- 

 trum from which blue and violet are omitted. Jaeger, the naturalist, 

 states that the Elaters were frequently the means of saving his life, 

 by lighting his way out of the dense forests of St. Domingo. 



FIG. 154. Diving-beetle (^Dytiscus margtnalts). ^ grub, showing pincers. 



Diving-Beetles {Dytiscida). These aquatic beetles 

 (Fig. 154) are of an oval or rounded form, with the pos- 

 terior legs fringed for swimming, and feet provided with 

 suckers (Fig. 155). The larvae are ferocious creatures, 

 called water-tigers (Fig. 154, g), having flattened heads and 

 scissor-like jaws, with which they capture small fishes, tad- 

 poles, and insects. The body ends in a pair of respiratory 

 tubes, that are thrust into the air. When ready to change, 

 the larva creeps ashore, builds a round cell, and in five 

 10 



