OF SOME DIURNAL LEPIDOPTERA. 67 



on Pieris Agathina and P. Chloris, two West- African But- 

 terflies ; and no approach to this form has been discovered 

 on any others. The figui'e drawn by Mr. Sidebotham 

 (fig. 15) gives a very correct idea of the reality; but the 

 study of the actual objects with the binocular microscope 

 and high powers will be well rewarded, and give abundant 

 cause for speculation as to the absolute form of the plu- 

 mules. They appear to be hollow membranous bags of a 

 cylindrical or triangular shape_, bound round by longitu- 

 dinal ribs, which are curved inwardly, forming a contrac- 

 tion at about one-half or one-third of their length, where 

 they are drawn in as by a cord. At the base, the ribs 

 are inflexed towards the peduncle and bulb, to which they 

 seem attached by the membrane. The large double-lobed 

 transparent bulb, besides acting as a ball-and-socket 

 joint, seems to serve as a valve to close the bag. Above 

 the contraction, the ribs are continued with a curvature 

 similar to the lower portion, and terminate in extremely 

 fine and delicate points. In difierent specimens these 

 approach more or less closely, and they appear to be free 

 at the upper extremity, with a power of contraction or 

 closing to protect the interior of the bag from the entrance 

 of injurious matter. Their appearance is very much like 

 that of the ciliated tentacula of the Stephanoceros or 

 peristomes of some of the Mosses. The length of the 

 bag is about i -300th of an inch, without the peduncle 

 and bulb, which, when fully drawn out, extend about 

 I -Sooth of an inch further beyond the point of attach- 

 ment. Passing from the Pieridse to the very extensive 

 family Nymphalidae, it must be noticed that the plumules 

 have only been discovered on one genus, viz. Argynnis. 

 The type or character of form is very distinct from any in 

 the Pieridse ; but all the species examined exhibit generic 

 resemblance and specific variety; and it is probable that 

 the plumules may be discovered in other genera. 



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