416 



KNOWLEDGE. 



October, lOlO. 





^ 



Figure 1. Fan-shaped scales of Hahrosfdla, 

 16 mm. 



the scale, or to the irregular disposition of the dots. This 

 appearance may be seen by viewing the more highly magnified 



figure obliquely. The longi- 

 tudinal striae, it will be seen, 

 are closer in the elongate oval 

 scales. The dots occur along 

 the striae, and in the interspaces, 

 where they gi\e rise to an 

 appearance of transverse stria- 

 tion. more clearly marked in 

 some other species. There may 

 be a real transverse striation, 

 as well, in which all the lines 

 are not parallel, but seem like a 

 series of I's, while occasionally 

 V'sand _ 



V's oc- 

 cur; in 

 such 



Figure 2. Part of a fan- 

 shaped scale of Habrostula, 

 2 nun. 



cases 

 there is 



a dot at the angular junction of the 

 V or Y. The appearances then sug- 

 gest that the dots are connected by 

 tubules, which appear to be curved, 

 and resemble, on a much smaller 

 scale, the pseudotracheal tubes in a 

 fly's tongue. The real significance of 

 these markings does not seem to be 

 yet understood ; but almost all insect 

 scales are probably to be reduced to 

 the same type, so far as 

 their markings are con- 

 cerned. With regard to 

 the shapes assumed by 

 insect scales and hairs, it 

 would be valuable to have 

 a kind of census made, 

 showing their distribu- 

 tion. Some forms show 

 only one or two types, 

 while others may have six 

 or seven ; it may be 

 possible to draw some 

 phylogenetic inferences 

 from the facts, when thor- 

 oughly ascertained and 

 tabulated ; or, if not, we 

 should have a proof of 

 the independent evolu- 

 tion of similar organs. 

 Hahrostola,iox example, 

 has many scales of a type 

 which is most prevalent 

 in the Vanessidae. The 

 scales of the Zygaenids 



Figure 4. Part of an (i\al 



elongate scale of Htibro- 



stola. showing watered silk 



appearance, 2 mm. 



I-IGI-Ric 3. Fart ot another oval elongate scale 



of Habrostola showing watered silk appearance. 



2 mm. 



Scales of Arj^ynnis, 



r^lGURE J. ( )val elongate scales of Hahntstvla. showing 

 watered silk appearance. 16 mm. 



are as uniform in the individual species as any that I have yet 

 examined ; yet related species have, in that tribe, scales of 

 distinct forms. Some sixteen 

 years ago, by the kindness of 

 Mr. J. \\'. Tutt, I was enabled to 

 examine the scales of a large 

 number of .Mpine Zygaenids, 

 with the result just mentioned ; 

 a partial report of the matter 

 then appeared in The Enio- 

 iiiologist's Record. For such a 

 census as I have suggested, 

 it would be advisable to 

 construct a system of nomen- 

 clature for the different types of 

 scales, 

 and 

 this 

 should 

 not be 

 d o n e 

 until 

 t h e 



number of types and their approxi- 

 mate occurrence is known with 

 greater certainty than at present. 

 ( )ne might begin, therefore, by naming 

 the principal known types with letters 

 or figures, to be exchanged afterwards 

 for appropriate and definitory terms. 

 Perhaps some readers of Know- 

 ledge may see their way 

 to assist in this prelimin- 

 ary work ; I may mention 

 that my address is 21, 

 Princess-road, South 

 Norwood, S.E. .4s to 

 the methods of micro- 

 scopical manipulation of 

 insect scales, I now find 

 it best to make a pre- 

 liminarv examination of 

 the entire insect, fresh 

 if possible, and remove 

 samples of the different 

 scales separately. These 

 are placed for further 

 examination in a minimal 

 i|uantity of the mounting 

 medium (alcohol and 

 glycerin) ; I have just 

 found that cedar oil is 

 \ ery good, and it is cer- 

 tainly to be preferred on 

 grounds of optical theory. 

 E. \V. Boweli.. 



comparison. 



