52 



a cuticular membrane, consisting, of course, of an upper and lower lam- 

 ina, united at their edges and continued on the pedicel. Burmeis- 

 ter gives it as his opinion that the scale is empty between the two 

 laminae 5 but we cannot accept his view, becaase in those scales we 

 have examined there is always an internal pulp, which often contains 

 coloring matters. The scales have longitudinal striae, which are pro- 

 duced by folds of the outer surface or lamina, as is at once shown by a 

 cross-section of a scale (Plate IX, Fig. lA). The upper surface is more 

 nearly flat. The lower surface is recurved on each side. The scales are 

 thickest in the middle line and thin out towards the edges. All these fea- 

 tures were likewise observed by Bnrgess in Danais, and it is probable that 

 they are common to the majority of the lepidopterons scales. There has 

 been much dispute concerning the nature of the striae on the scales, and 

 Burgess was the first to describe their real character. Certainly Burmeis- 

 ter is in error when he says : "II n'estpas douteux que les stries bien visi- 

 bles des ^cailles soient des filets eleves an c6t(S interne de la lame superi- 

 eure, se pronongantau c6t6 externe seulement comme stries finementim- 

 primees."* In many species, especially of butterflies, there are trans- 

 verse striae, which are said by Burmeister to be confined to the inferior 

 lamina. In conjunction with the longitudinal striae, they divide the 

 scales into little squares. There is great variety in the form of the 

 scales, but the study of these variations has hitherto borne little fruit. 

 E. Schneider has published a memoir f on the form and distribution of 

 the scales over the body in Lepidoptera, treating the subject with con- 

 siderable detail. More interesting is Burmeister's essay, which con- 

 tains the best general account with which we are acquainted. 



The scales are inserted into peculiarly-shaped oblique i)ore-canals 

 (Plate XI, Fig. 5). They begin on the outer surface with a wide open 

 funnel that leads into a bulb or spherical dilatation of the pore. From 

 the deep-lying surface of the bulb runs inward a fine tube. Appar- 

 ently the stalk of the scale fits into the outer funnel, and is* attached to 

 the bulb. 



The distribution of the scale pores is characteristic 5 they lie in little 

 groups, which tend to spread out in lines having the same general trend, 

 but never strictly parallel with one another (Plate XI, Fig. 4). On the 

 legs, as already mentioned, there is a similar grouping, though not 

 identical with that shown in Fig. 4. On certain parts, as, for example, 

 the i)atagia and the membranous portions of the thoracic crust, the 

 pores are scattered more evenly, each by itself. 



The best account of the structure of the maxillae, or proboscis, of but- 

 terflies is that given by Burgess, and an examination of this organ in 

 Aletia reveals the same essential structure as in the butterfly, so that 

 we may dispense with a detailed account. Plate XI, Fig. 6, represents 



* H. Burmeister. Description physique de la E6publique Argentine. Tome cinqui^me. L6pido- 

 pt6re3. (Exaraen sp6cial des ^^caUles, pp. 21-28.) Bu6nos-Ayres, 1878. 



t R. Schneider. Die Schuppen an den verschiedenen Fliigel- und Korpertlieilen der Lepido- 

 pteren. Zeitsclir. f. d. gesammt. Nat.-Wiss. Ill (1878), pp. 1-59, Taf. l-HL. 



