THE DRAGON FLIES. 



143 



that in some places they are collected and used as manure. As their mouths are rudimentary they 

 can take no food in the perfect state, and their sole business is the perpetuation of their kind. 

 For this purpose the eggs are dropped into the water, being set free, in some instances at any rate, 

 by the disruption of the abdomen of the mother. 



The development of the larvae always takes place in the water, and they frequent both streams 

 and still water. The larva) are not very like the perfect insects, and have a depressed body, long, 

 bristle-shaped antennae, long plumose caudal bristles, and a series of paired branchial leaflets appended 

 to the sides of the . abdominal segments. They differ farther from the imago 

 in the powerful development of their mouths, and in accordance with this they 

 appear to be exceedingly predaceous in their habits. The larvae of the smaller 

 species usually live freely in the water, but those of many of the 

 larger ones burrow most ingeniously into the banks of the stream 

 f>\- pond that they inhabit, making a sort of U-shaped double 

 .gallery with two openings to the water, which flows into them, 

 so that the inmate can go in and out without the inconvenience 

 .of turning jn his abode. If the insects of this family have but a 

 short existence in the perfect state, they make up for this by 

 .considerably longevity in their earlier stages, which appear 

 .usually ,to occupy two or three years, during which the changes 

 of skin are very numerous. Sir John Lubbock found that a small 

 two-winged species (Cloeon dimidiaturn) moulted twenty times 

 in the course gf its aquatic existence, and that each moult was 

 .associated with greater or less structural changes, until the final 

 condition in which, the wings have attained considerable develop- 

 ment within their cases. The stage succeeding this is, however, 

 ,the most extraordinary in the life of the insect. The creature 

 .that emerges from the so-called " nymph " is apparently an 

 imago, and is able to use its wings sufficiently to fly to some resting-place, but it is not yet quite 

 mature ; all its parts are covered by an exceedingly delicate pilose pellicle, which completely masks 

 the true colour of the perfect insect, and has still to be stripped off before the imago appears. This 

 '" subimagq," or "pseudirnago," as it has been called, attaches itself to various objects on the shore, 

 -such as the trunks of (trees, palings, the stems and leaves of grasses and other plants, and even the 

 .clothes of passers-by then, after a longer or shorter interval, the outer pellicle is ruptured and the 

 ; insect comes foj-th, w^th brighter wings and much longer caudal bristles, and flies away, leaving the 

 .delicate skin s^ljl clingjug by its claws to the chosen resting-place. 



Of British s[>ecies of this group the best known are the May Flies (Ephemera vulgata), of which 

 the subimago is called the Green Drake and the imago the Grey Drake by anglers. These are large 

 species. The little two-winged Cloeon diptera and several species of Baetis in which, as in Cloeon, 

 ithere are only two caudal bristles, are also common. 



FAMILY XIII. LIBELLULID^, OR DRAGON FLIES. 



In this second family of the Subulicornia, the hind wings, as already stated, are approximately of 

 the same size as the anterior pair, a character which at once serves to distinguish them from the 

 Ephemeridse. The insects have a large broad head very freely attached to the thorax, and large, 

 convex, prominent eyes, which often meet upon the crown of the head, and have the facets of the 

 upper part larger than those of the lower. Between the eyes are three ocelli, two of which always 

 rest upon the vertex, and the third sometimes upon a bulbous projection of the front of the head, above 

 which originate the short., iiwl-shaped antenna?, consisting of six or seven joints, of which the first two 

 or three are stouter than the rest. The large labrum conceals the other organs of the mouth, which 

 consist of a pair of strong, horny, toothed mandibles, and a pair of maxillae, showing a single horny lobe, 

 and a palpus of one joint, unless the palpus be really wanting, and the organ usually so called 

 represent the galea. The mouth is closed below by a broad labium, which is of peculiar construc- 

 tion, the oute.r ,lpbes .being amalgamated with the two-jointed palpi, and the inner lobes either 



LARVA (A) AND PUPA (K) OF EPHEMERA 

 VL'LGAIA. 



