(j4 Kansas university quarterly. 



the cuticle of the epidermis of the antenna or wing fuses with it; tlie 

 thin stallc of the scale which unites the scale with its parent cell 

 secretes for a short distance between the cells of the epidermis such 

 a thickened layer as renders the joining of the scale with its support- 

 ing membrane much more secure. At first one sees on the scales only 

 a simple membrane, but soon longitudinal stri;\; develop in the follow- 

 ing manner: at certain places a further thickening takes place on the 

 secreting membrane, and proceeds till finally further dei)0siting is 

 limited to cross-stria; which develop between the sejjarate longitudinal 

 stride. The scale is now complete except for the pigment, which in 

 many species is deposited in the scale before its extrusion. 



After the scale is fully developed, the parent-cell disappears, the 

 granular content of the scale becomes absorbed, the primitive cell 

 membrane dies out, and there remains only the chitinized cuticle of 

 the scale, with its root fast in a pouch in the membrane. 



The striking analogies between the course of development of scales 

 and the varying conditions of the scales on the fully developed wing 

 can not escape the reader's attention. It is to be noted that Semper's 

 description of the formation of the insertion cups differs from that 

 given by Landois, and quoted aii/ea. 



While a typical method of transition from scale-hair to flattened 

 scale has been described on page 5S, a study of the scales of various 

 l,epidoi)terous forms reveals the fact that the transition from scale- 

 hair to Hat scale may follow other lines of gradation: that different 

 modes of development of the scales are apparent in different groups 

 of moths and butterflies: in a word that the scales present distinct 

 lines of specialization which possess characteristics sufficiently marked 

 to be recognizable by the student, and therefore to be to some extent 

 available in taxonomic work. 



The line of specialization exhibited by the scales of the Megalo- 

 pygidse is characterized by a splitting apart of the distal extremity of 

 the scale-hair into two or more fingers, then a growing palmation 

 between the fingers accompanied by a shortening of the proximal 

 ])ortion of the hair and of the distal fingers. The most specialized 

 form in this line is a sub-triangular scale with apex at pedicel and the 

 outer border or base of the triangle prolonged into three or four 

 rather long fingers. The transition forms are well shown in figure 10. 



Quite different is the line of specialization of the scales of the 

 Cossidae. The mode of transition from generalized form to special- 

 ized form can be observed on the hindwings of Prionoxystus robinicB. 

 Here the scale-hair first widens and flattens at its distal end; there is 

 then a gradual shortening and an expansion for a considerable dis- 

 tance behind the tip so that there is formed an elongate sub-spatulate 



