INTERNAL ANATOMY OF INSECTS. 163 



but as it is infinitely more slender, when in repose it is 

 rolled up spirally and concealed within the abdomen. 

 It is the puncture of this minute organ that produces the 

 curious galls formerly described to you a . But the most 

 anomalous ovipositor in this Order appears to be that 

 of Chrysis (C. ignita, &c.), which is covered by several 

 demi-tubes or scales enveloping and sliding over each 

 other : when these scales are removed, the true ovipositor 

 appears, which is of a structure similar to that of the rest 

 of the Order, but the valves are long and slender with 

 their summit generally visible without the anus b . 



Though the ovipositor of the majority of Dipterous in- 

 sects is a tube with retractile joints c , in the crane-flies 

 this organ is different, and, like that of Acrida above de- 

 scribed, consists of what at first sight appear two valves, 

 but each of which is formed of two pieces, the upper 

 ones sharp and longer, and the lower pair blunt. The 

 upper pair forms the auger that bores a hole in the 

 ground, and the lower conducts the eggs into it after it 

 is bored d . 



In the Aptera and Arachnida in general there seems 

 no remarkable instrument of this kind ; but Treviranus 

 has described one in spiders for extruding the eggs of a 

 singular construction. It is an oval plate lying between 

 the external genitals and spinning organs, and is com- 

 posed of a number of small screw-shaped cartilages, con- 

 nected together in the most wonderful manner. There 

 are few organs, he observes, in the animal kingdom which 



a See above, VOL. I. 448. 



" De Geer ii. 835. t. xxviii./ 20, 21. PLATE XV. FIG. 22. This 

 figure was drawn by a friend the organ seems more exerted than in 

 De Geer's. I cannot make out the little appendage at the end. 



c PLATE XVI. FIG. 2, 3. d Reaum. v, 19. t. iii./. 3-6. 



M 2 



