KELLOGC;: TAXONOMIC VALUE OF SCALES OF LEPIDOrTERA. 73 



covering on the under sides of hindwings in butterflies little or not at 

 all less specialized than that of the upper side of the forewings. 

 Such a condition is rarely found among the moths where the under 

 sides of the hindwings are much less important as a pattern-carr3'ing 

 surface. To be sure the specialization of the scales as a whole on 

 the wings of butterflies, front and hindwings, upp r and lower sides, 

 is much more advanced than almost any scale-contlition among the 

 moths, but the difference in degree of specialization between the 

 scales of the forewings of butterflies is much less than the difference 

 between the scale-specialization of the fore and hindwings of moths, 

 while the difference between the importance of the flight-function in 

 the fore and hindwings of butterflies as indicated by the venation is 

 approximately equivalent to the usual difference in flight-function 

 between the fore and hindwings of moths. 



The clear spaces in the wings of certain moths and butterflies, as 

 the Sesiidaa and certain Zygaenids and Heliconids, are to be explained, 

 not by presuming a generalized condition, a primitive state in which 

 scales have not yet developed, but rather a specialization by degra- 

 dation for purposes of ornamentation or imitation. The most gener- 

 alized Lepidoptera possess scales, and in addition a covering of fine, 

 fixed hairs. The forms possessing these clear areas are among the 

 more specialized Lepidoptera, and therefore if without scales must 

 have lost them. The clear areas never exhibit a covering of fine, 

 fixed hairs. The statements of various writers* tliat these clear 

 spaces in certain forms (as Helicoui(i) are sparsely covered with hairs, 

 is true, if we bear in mind that these "hairs" are the generalized 

 scales, always inserted in insertion cups, and wherever at all flattened 

 showing the characteristic longitudinal striation of the scale. 



In an exotic Heliconian, the wings, mostly clear, show a covering 

 of comparatively widely scattered scale-hairs, gr'adating into the 

 specialized scales of the scaled areas of the wings, but there are no 

 fine, fixed hairs (i. e., as those of the Jugata^ and the Trichoptera) 

 present in these clear areas. The scales in these clear areas have 

 faded out, and in so doing exhibit a series of gradatory scale-forms, 

 by retrogression, which may illustrate the mode of original progression 

 of specialization of the scales in these lepidopterous forms. A grada- 

 tory series of scales from the exotic Heliconian just referred to is 

 shown in figure 13, page 67. Among the butterflies, the scales are so 



*Kirby ;ind Spence say (Introduction to Entomology, voL 2. p. 0») : •• But th(in<-li the 

 general clothing of the wings of Lepidoptera consists of these liitlf scales vet in some 

 cases they are either replaced by hairs <n- mixed with them. Thus in tlie ele'ai- parts of 

 the wings of Heliconians, Attaci. etc.. short meonspietious hairs areplanieil- in a large 

 number of the orders the upper side of the anal area of the secondary wings is hairy" 

 The authors here refer to the scale-hairs, the scale in its generalized" or degraded condi- 

 tion. 



Burmeister similarly calls attention to the hairs (-'uoiis "j in the clear areas of the 

 wings of Ithomyiia, a clear-winged Heliconid. 



