OR THOPTERA. 1 6 9 



of their lower lip is not divided in front, and not exceeded in length by the 



palpi ; while each of the latter is armed with a strong tooth or spine. The 



abdomen is long, narrow, and cylindrical. Their larvae are more elongate, and 



have bigger eyes than those of the last family. The flat mask has the palpi narrow, 



and armed with a movable hook at the tip. Like the larvae of the Libellulidce 



they are provided with intestinal gills. Some of the largest dragon-flies belong to 



this family. 



The Agrionidce form a family of slender - bodied dragon - flies, which have 



both pairs of wings shaped nearly alike. They are further distinguished from the 



other two families by the shape of the head, the smaller size of the eyes, and 



the structure of the lower lip. The head has a projection at each side, at the 



end of which is placed one of the two hemispherical eyes ; and on the wide space, 



lying between the compound eyes, there are three ocelli arranged in a triangle. 



The lower lip consists at its free end of three parts of nearly equal length ; the 



median piece (ligula) being notched in the middle, while the two palpi consist of 



two joints, of which the first is large and terminates in an inwardly curved spine, 



whereas the second is small and articulated with the first, outside the base of its 



spine. The larvae may be known by the three leaf-like tracheal gills at the end of 



their body, which are wanting or inconspicuous in those of the other families. This 



family contains many of the most brilliantly and variously coloured dragon-flies ; 



the sexes of the same species often differing in coloration. Some of the exotic 



species attain a great length, but this is brought about by the elongation of their 



slender abdomen without a corresponding increase in the proportions of the other 



parts of the body. 



The day-flies, or May-flies (Ephemeridce), constituting the second 

 May-Flies. . 



group of the Pseudoneuroptera, are comprised in a single family. 



They have soft and fragile bodies, with a long ten-jointed abdomen, bearing at the 



extremity two or three long, bristle-like, and many-jointed tails. The hind-wings 



are sometimes wanting, and, when present, are always much smaller than the front 



pair, the latter being usually three-sided, with the corners rounded off. Three 



ocelli, in addition to the two large compound eyes, are borne upon the head ; and 



the antennas are short, and composed of two stout basal joints, followed by a slender, 



many-jointed bristle. In the adult the mouth-organs are never well developed, 



but remain small and soft. The jaws have no function to perform, as the perfect 



insects do not eat, but devote entirely to other pursuits the short span of life 



remaining to them. The common notion that the life of the May-flies in the winged 



state lasts but a single day is sometimes, but not generally, true, many being able 



to live several days, provided the atmosphere be not too dry. There are some. 



however, which do not live for even the proverbial day, but emerge one evening, 



only to perish before the sun again appears. There is less truth in the supposition 



that these insects appear only in May; May-flies of one species or another being 



seen on fine days throughout the summer and autumn. They are to be found in 



the neighbourhood of rivers and lakes, some Hying only by night, and others during 



the cooler hours of sunlight, or on favourable evenings until a little after sunset. 



During the heat of the day they seek repose, with their wings raised vertically. 



If the day be cold and raw. they seldom fly, but remain under shelter. In fine 



