WHIRLIGIG BEETLES. 39 



terminal segment is furnished with two pairs of similar but much 

 longer appendages. These filaments are employed as organs of 

 respiration, each being internally provided with a delicate air- 

 vessel, connected at the base with the ordinary lateral tracheae. 

 The body is terminated by four minute conical points, bent down- 

 wards, and which are used by the insect when in motion ; whereas 

 the long filaments have no peculiar motion. When the larva has 

 attained its full size at the beginning of August, it creeps out of 

 the water up the stems of the rushes or other aquatic plants, 

 where it encloses itself in an oval cocoon, pointed at each end, 

 composed of a substance spun out of its own body, and somewhat 

 resembling grey paper, within which it becomes a pupa. In this 

 condition it remains about a month, when it makes its appearance 

 in the perfect state, and immediately resorts to its native element, 

 the neighbouring water." 



Such is the life-history and description of the larva given by 

 Westwood, which appear not to be the result of his own observa- 

 tions, but largely, if not entirely, taken from those of De Geer. 

 I have never seen this larva, but expect it is an exceedingly 

 interesting microscopic object, and one which cannot be rare or 

 very difficult to obtain. Our entomological readers will do well 

 to be on the look-out for it another season. 



EXPLANATION OF PLATE IL 



Fig. 1. — Larva of Gyrinus. 

 2.— Gyriiius natator. 

 3. — Dytiscus marginalis. 



4, 5.— Upper and underside of antenna of Gyrinus. 

 6.— Posterior leg of Gyrinus, with tarsus extended. 

 7. — Ditto, only partially closed. 

 8. — Tarsus of same, very much extended. 



