NEUROPTERA. — LIBELLULIDE. 37 
neration have been ordinarily described as of very complicated struc- 
ture, and as occupying the under surface of the base of the abdomen. 
They have been described in detail by De Geer, Reaumur, and espe- 
cially by Rathke. Burmeister, however (Manual of Entomol., p.218.), 
asserts that these organs are only those of excitement, and that the 
real male organs are placed within the ninth * abdominal segment, in 
an aperture closed by two valves on the ventral surface of this seg- 
ment ( fig. 62.9.). 
These insects are distributed over all parts of the globe; few, how- 
ever, exceed in beauty or size the inhabitants of our own country; a 
peculiarity common to other aquatic tribes. 
The elegant appearance of these insects on the wing; their varied 
colours, insome, of a rich blue (“the beautiful blue damsel-flies ” of 
Moore); their delicate gauze-like wings, and their rapid flight, must 
have attracted the attention of every one. During the hottest days 
of summer they are to be observed darting backwards and forwards in 
the air, especially in the neighbourhood, or over standing water, where 
they find an ample supply of food in the myriads of insects which are 
there generated. The admirable adaptation of the form of the various 
parts of the body, namely, the powerful structure of the mouth, large 
size of the eyes and wings, and length of the rudder-like abdomen, has 
been happily treated by Mr. Newman (Exé. Mag., vol.ii. p.67.). There 
is considerable diversity in the colours of the sexes of some of these 
insects, the males having the abdomen ofa lead blue, whilst the females 
are rich yellow-brown. In some of the Agrionides, the males, which 
fly over the water in swarms, are of a rich blue, with black wings, 
whilst the females are fine green, with colourless wings. (See also 
Schelver in Weidemann’s Arch. Zool., st. 2.) |The partiality of these 
insects for various colours is noticed by Mr. Patterson (Ext... Trans., 
vol. i. p. 82. app.). 
These insects live in the perfect state a considerable period. In 
the summer of 1833, I noticed, during several weeks, a solitary 
specimen of Anax formosa hawking over a small pond on Wands- 
worth Common ; and, from the rarity of the species, I have no doubt 
that it was the same insect. Mr. Ingall has mentioned to me an in- 
stance in which a specimen, destitute of a head, and of which the 
* Tt is in the eighth, and not the ninth, abdominal segment that these valves 
are placed. Burmeister’s mistake has evidently originated in the apparent articu- 
lation of the basal segment. 
D 3 
