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XVIII. Tlte secretion ofpotassiuni Jiydroxide by Dicranura 

 vinula {inuiyo), and the emergence of tJie imago from 

 the cocoon. By Oswald H. Latter, M.A., Assistant 

 Master at Charterhouse ; late Tutor of Keble College. 

 Communicated by Feederic Merrifield, F.E.S. 



[Read November 2nd, 1892.] 



The investigations of which I now publish the results 

 were undertaken at the instigation of Mr. F. Merrifield, 

 to whom I must at once acknowledge my utmost in- 

 debtedness, not only for his suggestion, but also for a 

 most generous supply of material wherewith to conduct 

 my experiments and observations. I must also thank 

 my colleague, the Eev. S. D. Titmas, for much kind 

 assistance and advice. 



More than forty-five years ago Mr. Merrifield observed 

 that the imago of D. vinula produced an alkaline fluid at 

 the time of emergence from the pupa. The observation 

 was, I believe, never published, and no further work, so 

 far as I am aware, has been done on the subject until, at 

 Mr. Merritield's suggestion, I undertook its continuance. 

 It is well known that the larva of D. vinula spins an 

 exceedingly hard cocoon, composed partly of a tough 

 semitransparent substance, which is, as I conceive it, 

 virtually a mass of agglutinated silk, and partly of 

 portions of bark gnawed off from the tree on which 

 the cocoon is constructed. The whole forms a hard 

 unyielding protection to the enclosed pupa. Notwith- 

 standing the character of this wall, the imago pierces it 

 at the proper season without difficulty. The means 

 whereby this is accomplished I hope to show in the 

 following pages. 



Two distinct points present themselves for investi- 

 gation. (1) The means by which the cocoon is softened ; 

 (2j the apparatus employed in tearing open the cocoon 

 when softened. 



TRANS. ENT. SUC. LOxND. lb'J2. — PART IV. (dEC.) 



