1891.] 



215 



snake's skin. What its meaning is, and why it shoukl be absent from the corres- 

 ponding part of tlio inner portion of the phite, which, like the usual run of chitinous 

 material, shows no structural details whatever, I cannot explain. 



The ovipositor when at rest is completely concealed within the sheath. Its 

 skeletal portion is represented, as in the case of the sheath, by the dorsal plate 

 only. It consists of two very long and narrow subplates, the separate halves, as I 

 take it, of the dorsal plate, but united at their extreme tip to form the solid 

 penetrating point of the instrument. The subplates have a thick inside vein, or 

 rather a double vein with a narrow intervening bit, and a thin outside blade ; the 

 latter at the inner end vanishes almost insensibly into the rod, and at the outer 

 end is gathered up into the sides of the trowel. The end of the instrument has 

 a very different appearance according to which way we look at it. Viewed from 

 above, it is sharp-pointed and conical ; but from the side it reminds one of a 

 garden trowel, that is to say, it is hollow, with the sides deepening as they extend 

 back from the point. Its edge is served with a few irregular and shallow indenta- 

 tions, fitting it the better for cutting its way into the acorn stalk. The visceral 

 tube ends immediately behind the trowel in a pair of large transparent flaps, which, 



I am inclined to think, embrace the 

 sides of the acorn stalk and guide the 

 point of the egg into the cavity pre- 

 pared for it. 



The ovipositor plate lies so close 

 under the sheath, and is so bound to it 

 by the soft tissues, that it is no easy 

 matter to separate them, and it can sel- 

 dom be done without mutilation of one 

 or both. I therefore give a figure of the 

 parts of A.fibidella (Fig. 8), in which 

 I fortunately succeeded, after division of 

 the soft parts, in slipping the plate from 

 under the sheath without material in- 

 jury to either, the only remaining bond 

 of connection being the fibres of the 

 protrudor muscles of the ovipositor. 

 It will be noticed that the form of the 

 sheaLh is distinctly (though not essen- 

 tially) different from what it is in 

 viridella, but there is much less differ- 

 ence in the subplates of the ovipositor, 

 and the diagram represents very well the character of these parts in viridella. 



{To he continued.) 



Fig. 8. — Ovipositor and sheath of A. fibulella. p.m , Protrudor muscles of ovipositor. 



