86 MODERN CLASSIFICATION OF INSECTS. 
and consisting of three lobes, of which the centre one is deeply cleft in 
Agrion * (fig. 62.15.), but entire in shna and Libellula xx ; the two 
lateral lobes are flat and horny, with an articulation at the base, and 
of a very large size in Libellula (fig. 62. 5.), meeting and slightly 
crossing each other in front of the middle lobe; at the inner anterior 
angle of these lateral lobes is a small horny point, accompanied, in 
fEshna( jig. 62.14.) and Agrion (fig. 62.15.), by a short inarticulated 
appendage.+ Within the mouth, the lingua (fig. 62.6.), or the palatum 
of Latreille, appears distinctly of a large size, leathery, vesicular, and 
villose. The prothorax is reduced to a very short and small piece ; 
whilst the meso- and metathorax (not the mesothcrax alone, as stated 
by Latreille, Gen. Cr., vol. iii. p. 180.), are large, subcylindrical, ver- 
tically compressed, and oblique; the wings are large, of equal size, 
and exceedingly closely reticulated; the anal angle of the posterior 
pair being often acuminated in the males. Van der Hoeven has pub- 
lished a short note relative to the distinctions existing in the neuration 
of the wings of /Eshna, Libellula, and Lindenia, consisting of a small 
triangular space inclosed by strong nerves near the base of the fore 
wings. A careful comparative examination of the nerves of the dif- 
ferent species will clearly prove its existence, not only in the fore 
wings, but also in the posterior wings, of all the Libellulides, with this 
difference, that in the posterior wings, a supplemental piece, forming 
the anal angle, is added, so that the cells, analogous to those of the anal 
angle of the fore wings, are pushed out of place. When at rest, they 
are either horizontally extended or carried erect over the abdomen ; 
the legs are short, slender, and armed with numerous slender spines ; 
the tarsi are 3-jointed, the basal joint being the smallest (fig. 62. 8.) ; 
the abdomen is long, and either lanceolate-depressed, or subcylindrical, 
armed at its extremity with folioles or hooked appendages, variable in 
form, both in the sexes and species. In the males, the organs of ge- 
* By this name I here more especially mean L. virgo, which is the true type of 
Agrion Fab.; although Leach injudiciously formed it into the genus Calepteryx, 
retaining Agrion for cther insects. 
t The singular construction of the labium renders the analogical investigation of 
its parts very difficult : we may regard these three lobes as forming a trilobed ligula, 
in which ease, however, the horny point at the internal angle of the lateral pieces 
must be regarded as appendages, and not as palpi, as Latreille regarded them ( Gen. 
Crust., vol. iii. p. 180.), because the labial palpi never arise from the extremity of the 
lateral lobes of the ligula, In such case, perhaps the outer part of the maxilla would 
rather represent the galea, the palpi being obsolete. On the other hand, we may, 
with M. Brullé (Ann. Soc. Ent. de France, tom. ii. p. 343.), regard the outer lobes 
as enormously dilated labial palpi. 
