256 



(Sci)tcmbor, IS'.il. 



off a pair of cliitiiious rods (Fig. 11, b), which at the otlier end run into, and arc 

 amalgamated wltli, the tip of the knife plate. These rods are the backs of the 

 supplementary knives. They possess blades (Fig. 11, o'), which are fibrous, like the 

 blades of the main knives. Each supplementary blade is united by its edge to the 

 same part of the corresponding main blade, their union giving rise to a thick solid 

 rim, which runs all round the knife plate, and out of the under-side of which at the 

 lancet-like end the saw is cut. 



Following the rule in cutting instruments, the visceral tube does not reach to 

 the end of the knife-plate, but leaves the cutting point free. A pair of rather large 

 lanceolate plates (Fig. 11 f) are imbedded in the wall of its lower side, the 

 points of which project a little beyond the mouth of the tube. I have little doubt 

 that they are the two halves of tiio ventral plate of the ovipositor (9th segment), 

 but quite dis- 

 located from - 9iov) 

 the rods, and 

 having no con- 

 nection with 

 them. Wliea 

 the tube is ool- 



lapsed, the Fio. 12. 



plates lay side by side, but when distended, they become widely separated, and 

 bring into view on the intervening membrane numbers of rather large recurved teetli 

 (Fig. 9, 1), which, by seizing hold of the wall of the pocket during the birth of tlie 

 egg, must, I imagine, greatly facilitate that process. The tactile hairs are confined to 

 the 7th or last abdominal segment, with the exception of a few short and very stiff 

 ones that are placed at pretty regular intervals along the edge of the knife plate. 

 In semipurpurella and unmiaculella there are three of these hairs on each side, but 

 in purpurella, which has a proportionately shorter instrument, there are but two. 



At the commencement of these articles I alluded to the difficulty usually 

 attending the demonstration of the retractor muscles in the rigid, long-roddcd 

 instruments. In Micropteryx it is otherwise. I have already pointed out the 

 retractors of the ovipositor and their insertion into the inner spurs at the base of 

 the rods ; but it is to an instructive preparation of Dr. Chapman's that I am indebted 

 for the demonstration of the retractor muscles connected with the outer rods. They 

 appear in the preparation as broken fibres attached to the tips of these rods, and 

 passing up into the abdomen ; running in an opposite direction to the protrudors, 

 their office must be to draw back the 7th ventral plate out of the mouth of the leaf- 

 pocket, into which it had been advanced by tlie protrudors, and to close the 

 abdominal outlet. 



I will now give wliat I take to bo the meaning of this singular 

 and complicated implement. But first let me draw attention to the 

 curve at the end of the knife plate, a sliape scarcely fitting it, it 

 seems, either for scratching through the cuticle at starting, since the 

 point would be turned away from the surface of the leaf, or for 



Fig. 12. — Side view of last throe sogineuts ; 9 aud 8 considerably but not fully extended, a, Ven- 

 tral aub-plato of ovipositor, b. Lower spur, c, Upper spur. J, luter-seginoutu.1 

 uiouibraiie. 



