112 PARTIAL OJIISMOLOGY. 



within the abdomen. The hooks of such tongs are of very different 

 construction. In Dolichopus* they are lamellate, and armed with 

 hooks at their end ; lanceolate with an obtuse apex in the Libellults, 

 narrow, round, and spinose upon their inner margin in many Noctuce ; 

 simple, almost straight, but suddenly curved at their extremity in 

 Locusta ; short, thick, cylindrical, with lobate appendages in Laphria 

 and Asilus. The last segment frequently takes a very different shape 

 in consequence of these appendages, in Tipula it is clavate, in Mt/opa, 

 conical, cheliform in Panorpa, &c. 



The appendages of the sexual organs of female insects consist almost 

 exclusively of more or less prominent ovipositors, by the aid of which 

 they more easily deposit their eggs in appropriate places. We distin- 

 guish their following chief varieties. 



1. The STING (aculeus, PI. XXIII. f. 5 18) is a thin, delicate, 

 finely-pointed tube, consisting of several valves, and which sometimes 

 projects from (Sirex} and is sometimes withdrawn within the abdomen 

 ( Vespu). This sting is never a simple horny spine, but always 

 consists of two or three pieces, the largest of which is barbed at 

 its extremity, and is longitudinally channelled (PI. XXIII. f. J, c, and 

 f. 12) to receive the rest (the same, f. 7> d, f/). It possesses, besides, 

 two lateral VALVES (valvulee, the same, f. 6, a, a), between which the 

 sting lies like a sword in its case. If the sting project beyond 

 the abdomen, they accompany it, but only in those insects in which it 

 lies freely exserted. In the bees and wasps, which use it also as 

 an offensive weapon, the valves remain within the abdomen during 

 its use. 



Latreille calls the freely projecting ovipositor the BORER (terebru). 



2. The TUBE (tubulus, PI. XXIV. f. 15) is a mere continuation of 

 the abdomen, which occurs in Chrysis and many Diptera, viz. the 

 house-fly. It consists of several cylindrical joints, which are united 

 by a soft membrane, and are retractile within each other, like the joints 

 of a telescope. This kind of ovipositor is found only in insects which 

 have but few abdominal segments, whence it is not improbable that 

 the joints of the tube are nothing else than segments of the abdomen 

 itself. 



3. The SHEATH (vagina, PI. XXIV. f. 10 ) consist of two long, convex 

 continuations of the abdomen, generally inclining upwards, which, when 



* Meigen. Zwcif., Vol. iv. PI. XXXVI. f. 21 



