ORTHO PTERA. 
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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 he 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. 
Ma Flies The day-flies, or May-flies (Ephemeridce), constituting the second 
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 antennae 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 flying 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 
