144 NATURAL HISTORY. 



separated or united into a single piece. The structure of the thorax is also peculiar. The prothorax 

 is small and ring-like, and the meso- and meta-thorax are of large size, and placed almost horizontally 

 one above the other, so that the true back to which the wings are attached is quite behind, and the 

 breast, with the legs, thrown forward towards the head. The wings are closely reticulated, and the 

 legs of moderate length and strength, and terminated by three-jointed tarsi. The abdomen is elongated, 

 sometimes very long and slender, and is composed of eleven segments, of which the last but one bears 

 a pair of unjointed claw-like or leaf-like appendages. 



These insects, which are for the most part of moderate or large size, constitute a very numerous 

 group, some fourteen hundred species having been described from all parts of the world. They are 

 numerous and abundant in temperate climates, but become still more so within the tropics, where also 



the finest species are met with. Nevertheless, 

 the warmer regions have not so much advan- 

 tage over extra-tropical countries in the case of 

 this group as of some others ; some of the 

 European and British species may vie in si/c 

 and colouring with all but a few of their exotic 

 relatives. 



Their habits are everywhere much the 

 same. Like the Ephemeridse they are gener- 

 ally found in the vicinity of water, in which 

 element their preparatory stages are passed, 

 but quite unlike those abstemious creatui'es } 



LIBELLULA DEPRESSA. they are exceedingly voracious in their habits, 



continually hawking about upon their long 



and powerful wings in pursuit of their prey, which consists entirely of weaker insects captured 

 in the air. Thanks to a particularly powerful arrangement of muscles and tendon-like pieces 

 contained in the large thoracic segments which bear the wings, those organs are capable of almost 

 incessant action, and the Dragon Flies may be seen throughout a summer's day continually sweeping 

 about over the surface of some pond or stream, or poising themselves motionless in the air from time to 

 time by excessively rapid vibrations of the wings. They rest at night, and sometimes by day,, 

 especially in dull, cloudy weather, upon the twigs of trees and bushes, and the stalks and leaves of 

 grasses and other plants, and it is singular to observe how easily the insect when thus resting 

 escapes observation, notwithstanding its considerable size and often striking coloration. Their- 

 courtship is one of the most singular points in their history. The male seizes the female by the neck 

 with the claspers appended to the last abdominal segment but one, and thus united the pair may 

 often be seen in flight. After a time the female curves the end of her abdomen forward until it 

 comes in contact with the second abdominal segment of the male, which is singularly inflated and 

 cleft, and contains an organ by means of which the fertilising male elements are introduced into the- 

 proper position for fecundating the eggs ; and what renders this arrangement still more singular is, 

 that in the male the ducts leading from the organs secreting the fertilising fluid open near the end of 

 the abdomen in the ninth segment, so that he must, before going in search of his mate, purposely 

 charge the reservoir in the second segment of his abdomen. After the completion of the process, the 

 pair usually separate, but in some instances the male continues to clasp the neck of the female, so as. 

 to assist her in flying over the surface of the water in order to deposit her eggs suitably. 



In their general form the Libellulidse present very considerable differences, and in accordance 

 with these we may distinguish three principal groups. In a very great number the head is. 

 short and transverse, forming a sort of cylindrical piece, on the two ends of which the eyes are 

 situated, separated by a wide crown on which the ocelli are placed ; the abdomen is cylindrical and 

 very slender ; and the wings, which are of equal size, are closed together over the back of the 

 abdomen in repose. These, forming the sub-family AGRIOXIDES, are the most elegant of all the species, 

 and it is no doubt in allusion to the graceful slenderness of their forms, and to the mode in which they 

 are as it were draped in gauze when their wings are closed, that French collectors have bestowed 

 upon the Dragon Flies in general the fanciful name of Demoiselles. Sevcr.il species are exceedingly- 



