KELLOGG: TAXONOMIC VALUE OF SCALES OF LEPIDOPTERA. 



51 



Fig. 6. 

 a. base of scale of Gloveria 

 arizonensis; b, base of scale 

 of Morpho sp. 



Tlie pedicel is usually plainly distinguished 

 from the blade of the scale, but in some 

 cases there is a gradual tapering of the 

 blade towards the base, a gradual fading out 

 of the striie and it is difficult to say where 

 the pedicel begins or the blade ends (see 

 fig. 6.). 



The histology of the lepidopterous scale 

 has been given considerable attention, not 

 only by microscopists attracted by the variety of design, the symmetry 

 of outline and fineness of marking, but also by histologists seeking 

 to reveal the intimate structure of these characteristic features of the 

 Lepidoptera. 



The scales are flattened sacs, composed of two membranes, enclos- 

 ing sometimes only air, sometimes pigment granules attached to the 

 inner face of one of the membranes, and sometimes (as observed in 

 cabinet specimens) the dry remains of what may have been during 

 life an internal pulp.* The strin; are confined to the outer membrane 

 (that farthest from the wing membrane) and are probably folds in this 

 outer membrane (see fig. 9). The stride are plainly elevated above 

 the inter-strial space. All scales, excepting some androconia, possess 

 these longitudinal strice, which traverse the scale from base to outer 

 margin and are very sharp, and separated from one another by equal 

 distances. The stride sometimes curve in at the lower angles of the 

 blade, converging toward the origin of the pedicel; in other cases 

 they fade out at these angles. In scales of Dainiis arcJiippus from 33 

 to 46 striie, averaging .002 mm. apart, are present on each scale. 

 Tliere would thus be 12,500 of these stride to the inch. On transpa- 

 rent scales from AlorpJio sp. the stri;-e were .0015 mm. to .002 mm. 

 apart, on opaque (pigment-bearing) scales from the same 

 specimen the striai were from .0007 mm. to .00072 mm. 

 apart or at the rate of about 35,000 to the inch. 



While these stria; are in most cases uniform in appear- 

 ance on a single scale, in a few instances there are a few 

 specially heavy and pronounced strire, each one terminat- 

 ing at the outer margin in a short point or tooth. These 

 striae are separated by equal distances, while between 

 them are ordinary fine longitudinal striffi. There is Scaieof Hepi- 



1 J J j-i- 1 • 1 ■, J u ^1^1** lucglash- 



thus produced an eftect which may be expressed by anil, showing 



... , , . 1 1 primary and 



attributing to the scale a primary and a secondary secondary 



slriation. 



*Minot and Burgess In their description of the anatomy of 'Aletia (Ith Kept. U. S. Eut. 

 Com.. 1885, Washingt')n) deciare thai in all of the scales examined by them there was 

 always an internal pnlp which contained culoriug matters. 



Fig. 7. 



