, is Transactions of the Society. 



specimens of this insect in Co. Antrim,* and this circumstance 

 presented a favourable opportunity for the study of its scales. 



(!> neral Appearance of the Scales. — Under the Microscope the 



general appearance of the scales is very similar to that of the more 



common Lepisma saccharina. In shape they are for the most part 



ovate and circular, with a regular indentation at the pedicle. In 



some scales there is also a slight indentation at the free end. Under 



low powers they present the familiar " watered-silk " appearance 



and iridescence. Under medium and high powers they show a 



shell-like structure, due to longitudinal stria?, which latter at the 



marginal portion of most of the scales are broken up into bead-like 



and cuneate markings resembling the " exclamation markings " of 



Podura scales. The area covered by these markings varies in size, 



being as a rule greater in the more circular scales. The striae in 



the central or median portion of the scales are almost invariably 



unbroken. Towards the pedicle the longitudinal stria? frequently 



stop short, revealing by their apparent absence another set of striae, 



crossing the scale obliquely in two directions and radiating from 



the pedicle and the median line of the scale. The oblique stria? 



appear to be slightly narrower than the longitudinal ones. A close 



examination of the scale with high powers (^ and y 1 ^ in.) clearly 



reveals, by varying the focus up and down, that the beaded and 



cuneate markings are produced, as first pointed out by R. Beck, 



by the intersection of the radial and the longitudinal stria?. The 



beaded markings occur at the margin towards the pedicle, where 



the radial stria? cross the others at an angle approaching a right 



angle, but where the angle of crossing is more acute, towards the free 



end of the scale, the beaded markings change into the cuneate forms. 



Minute Structure of the Scales. — According to R. Beckf the 

 longitudinal stria? appear to project at the free margin of the scale, 

 thus suggesting a series of longitudinal ribs with corrugations 

 between the latter. This is quite true, but a careful examination 

 of the so-called ribs, towards the pedicle end of the scale, shows 

 that they are really the walls of a set of longitudinal tubes. When 

 pressure is applied to the scales these tubes may be made to collapse 

 and disappear to a certain extent, and in some cases when heat is 

 applied both liquid substances and air-bubbles are observed to 

 traverse the tubes. According to the observations of J. Beck the 

 longitudinal stria? are on the side of the scale next the insect, but 

 I hnd the reverse to be the case, thus supporting the later finding 

 of G. H. Bryan on this point.! The scales appear to be slightly 

 concavo-convex in shape, the longitudinal tubes being on the convex 

 side of the scale. On the concave side of the scale the pedicle has 



* New Irish Apterygota, by Prof. G. H. Carpenter, Irish Naturalist, May 1911, 

 p. 81. 



t Appendix to Sir J. Lubbock's Monograph on the Collembola and Thysanura, 

 Ray Soc, 1872. % Science Gossip, vii. N.S., pp. 152-4. 



