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These differ materially from those found on the pupseform or other sexual marks, and unlike the latter are not 

 restricted to the male sex. In the Ornithoptera a peculiar form of wing is associated with the presence of these scales ; 

 and the fragrance is scattered by long mobile tufts of scale hairs, or rubbed off by the so-called rubbing spots 

 (Reibeflecks) . In the Heterocerous Genus Hypsa other hard scales appear to produce a shrill sound. E. Haase speaks 

 of the scent organs, and remarks that they are defensively repellant, as in other Genera. They are sometimes scattered 

 on the wings, but a local arrangement is more common. The positions which they occupy among the Diurnal and 

 Heterocerous Lepidoptera are very varied, as I have shewn in Vol. I of this work, thus : — 



They are situated on the upper surface of the anterior wings of the Ulysses and Paris groups of Papilios as plumiform 

 stripes, parallel to some of the lower veins; also in Peranthus, and Argynnis ; on the undersurface in the beautiful 

 Bizones and Celerena ; often on the posterior wings only — in Erebus and Nyctipao on the costal margin of the posterior 

 wings, also in Argiva and Patula in a fold ; on the upper side of the wing in Eronia, Ideopsis, Danais, Amathusia, Ragadia, 

 &c. ; on the abdominal marginal area in Morpho ; on the lower surface in Plecoptera ; in a costal fold of the anterior 

 wings in some, of the Lyccznidce and Hesperiidce, and in a large aggregated mass on the femur and tibia of some of the 

 Erebidtz, and sometimes near the apex of the antennae of some Pyralidce ; on the thorax of Chcerocampa ; on the abdomen 

 in some of the Sphingidcs and Agaristidce, and also some Noctuse. In almost all Danaidcs, &c, they lie near the genital 

 aperture ; on the palpi in Berhda and some of the lovely Pyralidas, or on the ist pair of feet, also on the appendages in 

 Ismene of the Hesperid butterflies, Caprila, and Hyblcea among the noctuid moths, &c. The lines or striae on 

 some of the wing scales are often one-ioo,oooth of an inch thick; and Royston-Pigott says, "they are apparantly a 

 kind of flattened hairs, most of which are hollow, and similarly endowed with molecules containing an oily sap." If 

 this be so, it will go far to explain why certain species of Lepidoptera fade so terribly when exposed to the light, by the 

 chemical destruction of this oily material. Those species with colour-interference scales do not suffer much from this 

 cause. 



As I have shewn above, the scales of the Ornithoptera alone are so varied in form, that it would be difficult to 

 exhaust their possibilies ; to figure and describe all their variations in the Lepidoptera would require the united 

 lifetimes of several students. Dr. H. Burmeister, as the result of his study of the scales of the species of Castnia, which 

 are the largest of any insect, shows that they do not enclose any third membrane, but are empty, — the two membranes 

 of which they are composed do not touch each other, there being a certain space between them. The coloured ones 

 contain a coloured fluid at the commencement of the scale, which dies little by little by the action of the air, and leaves 

 a deposit on the inner surface of the two membranes, this fluid being finally replaced by the air entering through the 

 membranes, which remain soft for a short time after the formation of the scale. 



The colouring matter seems to be principally attached to the upper membrane, rendering it opaque, while the lower 

 one is more transparent from the absence or partial absence of the deposit. The longitudinal strias belong entirely to 

 the upper membrane of the scales, and are wanting in the lower. In the Ornithoptera I do not find that this rule 

 holds good ; for when examining broken scales, especially from the black areas of the wings, it is possible to easily 

 detect the same striss on the lower membrane ; and some of them can be seen through the upper membrane. The 

 breadth of the spaces between the lines is greater than that of the lines themselves. The lines are generally of equal 

 breadth, but sometimes a thick and thin line will alternate ; in some of the Ornithoptera these lines are duplicated 

 in both thicknesses, as are the latitudinal or transverse lines. The thick lines correspond to the teeth or indentations 

 of the margin (somewhat as the curved ribs of the Pecten shells of the Mollusca do), and the thin lines to the intervals 

 between them. The transverse lines which appear to divide the longitudinal into squares or trellis work are really 

 produced by the striae on the lower membrane showing through the upper one. Hence have originated many errors in 

 the appreciation of the structure of the scales. Dr. Royston-Pigott in investigating with a power of 3,000 the striated 

 surfaces of these scales, decided that though appearing approximately, they are really covered with villi, chenille or 

 velvet pile, teminating in a spherule ! the recognised object of these striae, regarded as corrugations, being to give 

 strength to a most delicate tissue, which are again supported by cross striae. " Upon the latter," he said, " are villi 

 erected upon them by twos and threes, and summits consisting of a refracting spherule." Later investigations however 

 have quite invalidated his theory, which was based on the study only of the scales of Vanessa Atalanta, The Red 

 Admirable. 



For a fuller study of this subject, reference may be made to the following bibliography: — 



Burmeister, " Physical Description of the Argentine Republic," Vol. V. Lepidopteres, part 1, page 21 (1878). 



