810 Transactions of the Societij. 



XXXVI. — Note 011 the Structure of the Scale of a Species of the 

 Genus Mormo. By Joseph Beck, F.K.M.S. 



iHead 8ih Odoher, 1879.) 



There is no subject which has been more freely discussed, and with 

 such varying conchisions (not even excepting the mnch- vexed 

 question of the structure of the sihceous valves of the Diatomaceas), 

 than that of the causes producing the apj^earance of " notes of 

 exclamation markings " on the scales of several of the Thysanura. 



It is not my intention to enter into a resume of the views held 

 by difierent microscopists, but simply to notice what I regard as a 

 fresh proof that these so-called " markings " are due to a structure 

 very dij&erent from what would be assumed were we merely to 

 judge from the appearances that are apparent under the Microscope. 



For some years I have maintained that the " notes of exclama- 

 tion " markings on the scales of Lepidocyrtis are due to uneven 

 corrugations in the membranes of which they are composed, and I 

 have illustrated this before the Society by running moisture up 

 and down the scale in the furrows between the corrugations or 

 ridges. In the supplement to Sir John Lubbock's treatise on the 

 Thysanura, I have used these words in describing the scale of 

 Lep)iclocyrtis curvicollis, " Irregular striae or corrugations from 

 pedicle to apex broken up into large, well-defined separate ' notes of 

 exclamation ' markings ; markings very black, with a light bright 

 ridge down the centre of each ; appearance due to irregular 

 corrugations on the outer surface of the under membrane, slight 

 undulations on the outer surface of the upper membrane, and to 

 structure between the superposed membranes." I have produced 

 a similar appearance by rubbing together two scales of Polyom- 

 matus argus, which scales have straight simple ridges running 

 from pedicle to apex — when placed over one another at an angle* — 

 but I have never until now been able to find a moth or butterfly 

 scale which, in its natural condition, gave under the Microscope the 

 appearance of " notes of exclamation " markings. 



I now desire to caU the attention of the Society to a scale from 

 a specimen of the genus Mormo from the East Indies (I have been 

 unable to obtain the exact name, having only the wing), which 

 shows " notes of exclamation " markings very similar to those 

 observed on many of the Thysanura. IJnder a low power these 

 scales present the same watered-silk appearance seen in Lepidocyrtis 

 curvicollis ; under a ^ they show the " notes of exclamation " 

 markings ; under a yV ^^^1 ^^^ resolved into distinct ribs from pedicle 

 to apex, thus showing in one scale how tlie appearances run from 



* Sec Carpenter's 'The Microscope and i(s Revelations,' 5th edition (1875), 

 p. 695. 



