40 MODERN CLASSIFICATION OF iNSECTS. 
In the Agrionides the abdomen of the larve and pupe are termi- 
nated by three narrow elongated plates ( fig. 62. 19.. 
The preparatory states of these insects last for ten or eleven months ; 
during which, according to Latreille, the skin is cast several times (but 
Drury states that he had not observed this shedding of the skin). 
When nearly arrived at the period for assuming the perfect state, the 
wing-cases become detached from each other, and exhibit traces of 
the mesh-like appearance of the inclosed wings. The pupa creeps up 
the stem of some aquatic plant or stone, when about to assume the 
imago state; after a few hours remaining in this situation, it attaches 
itself as firmly as possible to the spot by means of its ungues, the 
head being uppermost ; the skin of the thorax then slits, and the in- 
closed pupa gradually disengages itself, throwing its head backwards ; 
which position it retains for a considerable period, being retained in 
its situation by the terminal rings of the abdomen, which remain still 
within the pupa skin; it then gains an erect position, draws out the 
remainder of the abdomen, and remains stationary for an hour or two, 
until its pendant wings have assumed their full size and consistence. 
Rosel has given figures of various species of Libellule, Aishn, and 
Agriones, in their different states (Ins. Belust., vol. ii.; Ins. Aq., 
tab. 2—11.); De Geer also (vol. ii.) ; Reaumur (Mémoires, vol. vi.) ; 
Lyonnet (Mém. Posth., pl. 18.) ; Guérin (Icon. R. An. Insectes) ; 
Frisch (vol. i. pt. 8. pl. 8.); Swammerdam (tab. 12.); and Drury 
(vol. i.), have given figures and descriptions of the preparatory states 
of various species of dragon flies. 
Fabricius formed these insects into a distinct class (order), named 
Odonata. 
Dr. Leach has divided them into two families; but it appears to 
me to be more natural to consider them constituting one family, cor- 
responding with the Linnzan genus, divisible into two subfamilies. 
The exotic species do not offer any material peculiarities, if we except 
some species of tropical Agrionides, which have the abdomen nearly 
six inches long, and very slender and cylindric. 
Dr. Leach also, many years ago, divided these insects into several ad- 
ditional genera, which have not been adopted by foreign writers; but I 
have little doubt that corresponding characters would be found to distin- 
guish the genera of Libellulides, in the preparatory stages, as well marked 
as those which I have noticed above in the genera of Agrionides. 

