Boyal Mtcroscojoical Society. 3 



II. — Notes on the Minute Structure of the Scales of Certain Insects. 

 By S. J. McIntiee, F.E.M.S. 



(^Read lefore the Eotal Microscopical Society, Nov. 9th, 1870.) 



Plates LXIX., LXX., LXXI. 



Dr. Pigott's paper on High-power Definition has caused me to 

 devote some further attention to the markings of the scales of 

 insects ; and as some of the results I have obtained in the examina- 

 tion of a very great number of scales fi'om all sorts of insects are 

 curious, it may be well to place them on record, since they may 

 prove as novel to a few readers as they were to me. 



The first fig. on Plate LXIX. represents the scale of one of our 

 hunting spiders, Scenicus salticus, the prettily-marked zebra-spider, 

 which has so often furnished a theme for natural history writers, 

 from its ingenuity in laying wait for and capturing its prey by an 

 accurate and sudden spring upon it — a process which may be easily 

 seen on any hot summer day on walls and pahngs fully exposed to 

 the sun. The scales are situated on all parts of its body and legs ; 

 and with some care, though not without difficulty, they may be de- 

 tached and examined under high powers. Their margin is beau- 

 tifully crenated, and the outer membrane is smooth, while the inner 

 membrane — that is, the membrane next the spider's body — is puck- 

 ered up into somewhat irregular rows of hackles. When I first found 

 this scale I was struck with its resemblance, though a distant one, to 

 the view which Mr. Beck entertained respecting the surface-contour 

 of the Podura scale (Lepidocyrtus). I could not help regarding it 

 as, to a certain extent, confirming his view that the " inteijection 

 markings " on that scale are elevations of the membrane. I am still 

 further strengthened in the notion since reading Sir John Lubbock's 

 latest observations upon the position which the Thysanura occupy 

 in relation to entomological classification. It would appear, from 

 the absence of tracheae in many of these creatures, the presence of 

 certain abdominal appendages (possibly representing extra legs), 

 the absence of metamorphosis, and some few other points, that this 

 authority is disposed to see in them a closer relationship to the 

 Arachnida and Myriapoda than to the Insecta. At all events, it 

 is clear that the peculiar hackle-like structure, which has been 

 asserted for the Lepidocyrtus scale, is not without a parallel among 

 the tegumentary appendages of the Articulata. 



Another very curious scale I found surrounding the eyes, and 

 various portions of the under-surface of one of the Chinese Curcu- 

 lionidse, Hypomeces squamosus.^ This scale is leaf-shaped; its 



* It would perhaps be correct to consider these two scales as imitating the 

 structure of compound hairs. 



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