THE I) RAG OX FLIES. 



14.3 



AGKION PUELLA. 



abundant in Britain. Agrlon puella in which the abdomen of the male is banded with azure 



blue, while that of the female is almost entirely brassy black, is an insect about an inch and a quarter 



long that occurs almost everywhere; and the beautiful 



Callepteryx viryo, of which the male is steel-blue with a 



large brown patch with steel-blue lustre on each wing, and 



the female rather greenish with brownish wings, is to be 



met with frequently about running waters. Some American 



species have the abdomen of inordinate length, extending 



far beyond the closed wings. These form the genera 



Meyaloprepes and Mecistoyaster, species of which attain the 



length of four or live inches. 



In a second group, that of the ^EscHMD.*:, the abdomen 

 is still cylindrical, but stouter in proportion than in the 

 Agrionides. The head also is large and nearly hemispherical 

 in form, and the eyes are enormous, usually covering the 

 whole upper and lateral surfaces, and meeting on the crown 

 in the middle line. The wings are always extended at the sides of the body. These are large and 

 strong insects, possessing a wonderful power of flight, and several species are common in Europe and 

 Britain. The Great Dragon Fly (^Eschna grandis) is one of these. It is nearly three inches long, 

 and is of a light rusty brown colour, with a few paler markings. Another is Gomphas 

 vulyatissimus, a black insect nearly two inches long, with yellow bands on the thorax and a line of 

 the same colour along the back of the abdomen. Some of the tropical species attain a considerably 

 larger size. 



Finally, in the true LIBELLULIDES we find the head, eyes, and wings showing the same general 

 characters as in the last group, but the abdomen is either broad and more or less flattened or 



comparatively slender, and then triangular in 

 section. In some forms the abdomen shows an 

 approach to the type of the ^Eschnides, but then 

 recourse may be had to a small character pre- 

 sented by the wings, which have a marked tri- 

 angular space a little way from the base, and 

 this is alike in both pairs of wings in the latter, 

 but different in the Libellulides. The best-known 

 English species of this group is the Libelhda 

 depressa, vulgarly known as the Horse Stinger, 

 an insect nearly two inches long, with a rather 

 broad depressed abdomen, which is yellowish- 

 brown with yellow spots on the sides in the 

 female, and coated with a beautiful violet-blue 

 powder in the male. It may be seen almost 

 everywhere hawking about over rivers and ponds." 

 The larvse of these different forms, although 

 not very closely resembling their parents, never- 

 NYMPH OF LIBELLULA, AND THE PERFECT INSECT EMERGING. theless differ from each other in general form, 



somewhat after the same fashion as the perfect 



insects, but all agree in one character, namely, that of being among the most predaceous of the insect 

 inhabitants of the water. The apparatus by which they capture their prey is of the same general 

 nature in all, and consists of a peculiar modification of the labium, which has been called the " mask." 

 In repose the chin-piece is folded back towards the breast, and to its extremity the broad labium is 

 attached by a hinge-joint, and the anterior margin of this bears a pair of forceps-like organs, repre- 

 senting the outer lobes of the labium united with the palpi, and articulated so as to close towards the 

 middle of the labium. Sometimes these terminal pieces are so large as to cover a great part of the 

 face when the labium is retracted ; in all cases the labium with its appendages completely closes the 

 257 



