NEUROPTERA. — LIBELLULID&> 39 
and 3dly, a pair of transversely triangular pieces, toothed along the inner 
margin, and articulated at the outer angles of the preceding piece, so 
as to be capable of being widely opened. The use of this curious in- 
strument, of which the insect has the power of opening and closing the 
various parts with the greatest facility, is to seize its prey, which 
consists of other aquatic insects, and even of small fishes (Mag. Nat. 
Hist., No. 28.), which are immediately brought within reach of the 
jaws. The parts of which this organ is composed are analogous in 
their general structure of the different groups, to those composing the 
lower lip of the imago ; thus, in Agrion virgo (fig. 62.15. labium of 
imago, fig. 62.17. labium of pupa), the central piece is deeply notched, 
and the lateral pieces are terminated by four acute spines.* (See Brullé, 
in Ann. Soc. Ent. de France, tom. ii. p. $43.) The basal part, by 
which this organ is attached to the head, appears to represent the 
mentum, the following more elongated piece, the labium (ligula), and 
the two terminal parts, the labial palpi. The sides of the meso- and 
meta-thorax are soldered together, and dilated into a large lateral plate. 
The mode of respiration in these insects during their preparatory 
states is singular. The abdomen is terminated, in the larger species, 
with five corneous plate-like appendages of unequal size, and conical 
form, three being much larger than the others, which the insect has 
the power of separating or bringing into contact, so as to form a py- 
ramidal tail. On opening these pieces, a valve, previously closed by 
three membranous plates, is opened, and a quantity of water passes 
into the body, when they are closed; shortly afterwards, however, the 
water, from which the insect has extracted the oxygen by the as- 
sistance of various internal organs communicating with the trachez, is 
discharged with considerable force to the distance of two or three 
inches, by the action of an inclosed organ, which Reaumur calls “le 
tampon.” This discharge has the effect of giving a progressive motion 
to the body. 
In the A‘shne the pupa has the middle plate at the extremity of the 
body truncated, and armed with two minute points. A memoir by 
Suckow, on the respiration in /Zshna grandis, is noticed in the Bulletin 
Sci. Nat., June, 1829. 
* In the genus Agrion (L. Puella), the mask of the larva ‘has a single projection 
on the upper edge of the mentum; in Lestes a double projection exists; and in Ca- 
lepteryx (L. virgo) it has a triangular excision at the tip, terminating in two points, 
( Stephen’s Brit, Ent., vol. vi. p. 78.) 
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