52 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
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 ; but we cannot accept his view, because 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. 1a). 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 Burgess in Danais, and it is probable that 
they are common to the majority of the lepidopterous 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 Bur tneis- 
terisin errorwhen he says: "Iln'estpasdouteuxqueles striesbien visi- 
bles des e'cailles soient des filets elevds au cote* interne de la lame superi- 
eure, se prononcant au cdte externeseulement comrae stries finement im- 
primdes."* In many species, especially of butterflies, there aje 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. 
R. 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 pore-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 j 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 patagia 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 
* U. Burmoistor. Description physique <lo la K6publique Argentine. Tome cinquieme. L6pido- 
pt6ros. (Exaiuen sp6cial des Readies, pp. 21-28.) 13u6nos-Ayro8, 1678. 
t R. Schneider. Die Schuppen an den verschiedonen Flttgol- und Korpertlioilen der Lepido- 
pteron. Zoitscbr. f. d. geaamnit. Nat.-Wiss. Ill (1878), pp. 1-59, Taf. I-IIL 
