138 NATURAL HISTORY OF 



GYRINUS, 



a word sometimes used by Aristotle and other Greek 

 writers, and which 13 devi/ed from a verb signifying 

 to move in a circle. They afford a few well-marked 

 characters, by which they are readily distinguished 

 from all their aquatic associates. The antennae are 

 ah:>rt and thick, and are attached to the head in 

 such a manner as to resemble ears. They consist 

 of a clavate mass formed of seven closely joined 

 rings, which is attached by a slender peduncle to 

 the upper and internal edge of a large radical joint 

 furnished with an auricle on its outer side, which, 

 like the lid of a box, shuts in the antennae when 

 unemployed, and protects them from the water.* 

 The anterior legs are long, and formed for walking, 

 or to act as instruments of prehension ; the four 

 hinder ones are very short, compressed and ciliated 

 externally, bearing a strong resemblance to the 

 paddle of an oar. The head is sunk in the thorax 

 as far as the eyes, and the latter are divided by a 

 process from the anterior part of the head, in such 

 a manner that there appear to be two eyes above 

 and two below a mode of structure admirably 

 adapted to the wants of the insect, which requires, 

 at the same time, to observe objects both in the air 

 and water. 



* Kirby and Spence's Introd. to Entom. iii. 516. 



