INSECTA. 421 



an efferent canal arising from two small vesicles filled with a yellow 

 fluid : these glands are wanting in Agrion 1 . The larvae and nymphs 

 live in the water, and resemble the perfect insects. The under-lip 

 has the form of a mask or hood, and covers the mouth j anteriorly it 

 terminates in two hooks 2 . It is bent round and set upon a long 

 flat pedicle, which the animal can move forward rapidly, whereon 

 the bending disappears ; thus the insect supplies itself with a move- 

 able forceps for seizing its prey unawares at a distance with the 

 hooks at the extremity of the under-lip. (See figures in SWAMMER- 

 DAM, Bibl. nat. Tab. xn. fig. 5, BEAUMUR, Ins. vi. PI. 36, fig. 4w, 

 figs. 1014, PI. 37, figs. 4, 6, 7, PI. 38, figs. 68, KCESEL, Ins. IL, 

 Ins. aquat. 01. II. Tab. in. figs. 76, fig. 8c, Tab. ix. figs. 3, 4 ; LYONET, 

 (Euvr. posthume, PI. 18, figs. 13 15). The abdomen of the larva 

 ends either with five horny plates, which can be moved from and to 

 each other, or with three fin-like laminae ; it was in these laminae 

 (in the genus Agrion) that CARUS first discovered the circulation of 

 the blood ; see above, p. 259. 



With LINNAEUS this family forms only a single genus, Libellula. 



Comp. on this family VAN DER LINDEN, Agriones Bononienses descriptte. 

 Opuscoli scientifici. Bologna, 1823, Tom. iv. p. 101 ; ejusd. JEshnce Bononi- 

 ciises, ibid. p. 158, &c. ; ejusd. Monographic^ Libellulinarum Europcearum 

 specimen. Bruxellis, 18-25 ; TOUSSAINT DE CHAEPENTIEE, Libellulince 

 EuropcecB descriptor et depictce, cum Tabulis 48 color. Lipsise 1840, 4to ; 

 E. DE SELYS LONGCHAMPS, Monographic des Libellulines d'Europe, Paris 

 et Bruxelles. 1840, 8vo; and the same author's different short communi- 

 cations in the 6th and 7th parts of the Bulletins de I'Acad. des Sc. de 

 Bruxelles. 



A. Intermediate lobe of labium very small, lateral lobes very 

 )road, without articulate style. 



Libellula FABR. Eyes large, often contiguous. Ocelli disposed 

 n a triangle. Wings horizontal, expanded, anterior different from 



1 Fuller information concerning these parts may be found in H. RATHKE, De 

 r jibellularum partibus yentialibus. Cum Tab. sen. in. Regiomonti, 1832. 4to. Because 

 ae penis is not connected with the tesles, of which the va*a defer entia terminate at the 

 linth ring of the abdomen, RATIIKE was of opinion that the union observed in the 

 jibelhdince is not a true copulation, but only precedes it. VON SIEBOLD, however, 

 ietected spermatozoa in the male at the base of the abdomen, so that the male, by 

 ending round the abdomen towards the thorax previous to copulation, seems to deposit 

 ae sperma there. WIEG MANN'S A rchiv f. Naturgesch. 1838, p. 375. 



2 These nippers are the palpi of the under-lip ; see A. BRULLE, Observations sur 

 i bouche des Libcllutincs, Ann. de la Soc. Entomol. 11. 1833, pp. 343 351, PI. 13. 



