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Psyche 4:43-47, 1883.

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PSYCHE.
THE SCALES OF COLEOPTERA.
BY GEORGE DIMMOCK, CAMBRIDGE, MASS.
(Confinued/rom page 27.)
The brown scales are lustreless and
without cross-bands, while the white
scales, as long as they are filled with
air, are silvery. This fact and other
reasons lead me to believe that the cross- bands are partial separations of the
lower lamina of the scale, and are the
cause of the silvery lustre of the white scales. I reserve, however, further dis- cussion of the production of silvery sur- faces for the last portion of this paper. To get at the finer structure of these
scales transverse sections of some of the brown ones were made; one of these
sections is shown in fig. 7. d. Altho
numerous sections as thin as 0.0025 mm.
were examined, I could find no longi-
tudinal canals or passages, but the lower Limina of the scale is somewhat more
transparent than the upper lamina ; on
the latter portion are the longitudinal
striae, seen in transverse section in fig. 7, d. Sections of the white scales are
similar in form, but are so transparent
in the fluids in which I was obliged to
study them that I tould find no air
cavities.
Treatment with reagents give positive
proof that both the white and brown
scales contain air. Alcohol or water
rapidly discharges air from cavities
within them ; glycerin expels it only less rapidly.
Scales regain their air readily
when dried from water or alcohol. Af-
ter treatment with any liquid the white
scales become very transparent, showing
that they contain no coloring matter ;
when mounted in Canada balsam they
are alinost invisible.
ELATERIDAE, SPECIES UNDETERMINED.
Fig. 8 represents the scales from an
undetermined species of elateridae,
from Leipzig, Germany. I figure them
here because I have found in no other
coleoptera scales of similar form. They
Fig. 8. Scales of :in undetermined species of dater- idae; a, seen from above; ?>, lateral -view. Enlarged 100 diam.
are, however, similar in structure to the brown scales of Alaus oculatus, but they have in addition a prolongation of the
distal end of the scale into a sort of short filament.
SCALES OF PTINUS ?RUTILUS.
A species of Rims, probably P. m-
ti'?us, which was found in great numbers Put-he 4 043-47 (pre-1903). hfp //psyche aitclub orgW4-0043 html



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("May-June 1883
in a dry-goods store in Leipzig, Ger-
many, furnishes interesting forms of
scales. Tins coleopteron is clothed with brown hairs, one of which is fignred
(fig. 9, c) and among these hairs are
scales (fig. 9, a and 6). The relative
size of the hairs and scales of this spe- cies of Rims may be seen from fig-. 9,
where both are drawn enlarged 100 di-
ameters. These scales have from two
to seven long apical points, are attached by a little stein at the base, and are 0.06 to 0.09 mm. in l e e by 0.01 to 0.03
mm. wide. Their color is light brown,
which is apparently produced, for the
most part, by somewhat irregular longi-
tudinal stripes or tl~ickei~ings upon the inner surface of the scales. These scales are filled with air.
Fig. 9.
Scsileb and hair of Pt/?ms ? ruit/its: n :ind 6, scales from elytron; c, hiiir from elytron. EnLtrged 100
diain.
SCALES OF CLYTUS ROBINIAE.
Nearly all the yellow stripes upon C.
mbiniae owe their entire coloration to
the scales with which they are covered.
This can be seen best by scraping all the @
scales from the insect, after which, with the exception of the legs and a few yel- low stripes on the elytra, it is black. Most black parts of the insect are, however,
improved in depth of color by being
clothed with black scales. The yellow
stripes upon the thorax are produced en- tirely by yellow scales which are set
upon a black background. The whole
richness of coloration of C. robiniae is pro~luccd by the scales with which it is clothed, as can perhaps be most strik-
i ltgly illustrated by removing the scales from one half of a specimen and leaving
the other half intact. I11 the siirne way the ground color of the European Sap-
crda scalaris is black, its beautiful col- oration being due to a dense coating of
scale-like hairs.
Fig. 10. Scale of Clytus robfniae. Enlarged 100 (1 i aim .
The black or brown scales from the
upper surface of the thorax or from the
elytra of C. robiniae resemble, at first glance, those of Maus ocda/us7 but
upon closer exainination they prove to
be quite different. Their form is approxi- mately an elongated parallelogram (see
fig. IO), with the shank or point of at- tachment at one of the acute angles.
The striae originate at and near the
shank and terminate along the opposite
end of the scale, thus diiTeringeiltirely in this respect, froth the sc.ilcs of AZazts. 7 7
J. he scales of C. robiniae are 0. I 5 to o. 18 1x111. long by about 0.02 mm. wide. Under the microscope they are dark
brown or light yellow, according to-
whether they are from the black or yel-
low parts of the insect. Both the yellow



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and the brown scales havo the same form
and structure, and both contain air, as
can be readily seen by the action of water upon them. Neither the brown nor the
yellow scales can be bleached by chlorin. Of the numerous scales of curculiw-
idae, the family of coleoptera in which
the possession of scales may be said to
be almost a rule, I have chosen for es-
pecial stidy the
SCALES OF ENTIMUS IMPERIALIS.
This species has the most brilliant,
and, in some respects, the roost interest- ing scales and hairs of any colcopteron
which 1 have examined. Nearly its
whole surface, above and beneath, is
covered with lines or masses of mil-lute Fig. n. Scales of Eniimus tfufieriuiis: on a, b and c vertical lines indicate blue, hoiiiontiil lines in&- catc cnrminc riid, and oblique lines yellow; where two kinds of lines cross, one color is tinffvd with theother; on d and t the fine lines represent the finer striation of the inner htyer of the bcale-s. Knlr~rgerncnt : 0, band e, 100 dim, ; d mid c, 300 diain.
scales, glistening by reflected light with the brightest colors, and these colors are heightened by the shining black back-
ground which the surface of the insect
affords. Hairs and scales cover its legs, and the hairs, as will be seen later, are of the same nature as are the scales.
The form of these appendages is
extremely variable. Their greatest
width is about 0.06 mm., and from this
width gradations may be found down
to hairs of a diameter of less than 0.01 mm. The length of such as are typi-
cally scales (fig. I I, a, b and c) is o. 15 too.18 mm. The hairs attain a length
of I .3 tnm.
Both hairs aid scales are colored in
the same way and with the same colors,
chiefly red, blue and yellow, by trans-
mitted light, and green and purple by
reflected light. Whatever the color by
reflected light, its cornpieineiitary color appears by transmitted light ; predomi-
nant is red by transmitted, and green
by reflected light. Thus one sees the
origin of the green color on the coleo-
pteron itself. Green, yellow, red, blue
and purple often appeiir on a single
scale, and these colors change if the
light is cliaiiget? from transmitted to
reflected ; they are especially bril-
liant upon a black background. Some
scales are of a single color, usually red. 011 figure I I, rt, (S and c, I have at- tempted, as far as is possible without
colored figures, to show the distribu-
tion of colors in three scales. Even
colored figures would have poorly re-
presented some of the brilliant variations which the scales present.
More careful miscroscopical exam i-
nation sufficed, even with tow powers,
to show that the scales have the ap-
pearance of being filled with p
inents, separate colors usually in d
tinct compartments allotted to them.
Sometimes, however, similar colors,
like yellow and yellowish red (see basal part of fig.
I I, a), or like blue and
purple, are in the same compartment.
Sorneti'mes there is a tinge of color near



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PSYCHE. [May-June tHS3.
the margin of a compartment different
rin or sulphuric anhydrid (SOn) fails
from the color of the middleof the corn- to bleach the scales ; acids and alkalies partment, as in the upper part of fig. II, do not change their colors.
Uninjured
b. The extreme margin of the scales
scales are not penetrated by liquids and is always transparent and colorless, and remain colored in th
sometimes, as if by a flaw, a little is surely due, then, transparent spot extends into the colored that is to some form
portion of the scale, as near the base of light.
fig. I I, c. At all points along the mar- The hairs are colo
gin where different compartments meet
scales, althou
the marginal transparent portion seems
to the naked
nifying powers a very thin, transparent
b
partition can be seen extending between
o
en filled with water the hairs a
different cornpartmen
liquidsfail to pass a
me part of a scale or hair colored after -.--1'L^- ---L l_-- L-*- -*-Jl^.--^3 L--- evident that, how-
:ions may be, they




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being so brittle that few can be removed without breaking. My experiments
were all made with scales from a speci-
men dried at least over ten years ; pos- sibly a fresh specimen would have less
brittle scales.
Further microscopic examination of
narrow scules and hairs reveals a longi- tudinal striation, the striae of which are from 0.0015 to 0.0020 mm. (or even
further) apart. This striation, which
for greater distinctness I will call the "coarser striation," is present on hairs, less marked on elongated scales, and
not generally observable on broad scales (such as represented in fig. I I, 6). This coarse striation is visible after the color has been removed from the scales and
hairs by reagents. It is easily seen to
be external on the cylindric.il hairs,
extending beyond the colored portion of
the hairs.
Still higher magnifying power brings to
view a second striation, which I will call the "finer striation." This striation was much more difficult to see than the coarser striation, the striae being very delicate and only 0.0008 to 0.0009 mm. apart.
Unlike the coarser striation, the finer
striation is more evident on broad scales and least evident or not discernible, at Ic~st with the objectives at my coin-
mnnd, on narrow scales and on hairs.
The finer striation is further unlike the coarser striation in following no definite direction on the scale, sometimes being
in one direction in one portion of a scale and in another direction in another part of the same scale. In any single com-
partment of a scale the direction of the finer striation is approximately the same, sometimes a
as seen under
rows of the
compartments
little curved, resembling,
the microscope, the fur-
finger-tips. In adjacent
I of a scale the finer striae
are sometimes at right angles to each
other, though oftener in the same direc- tion. I have attempted to represent,
on fig. 11, d and e, the finer striation upon two scales, but the striae, although proportionately about the right dis-
tance apart, are themselves relatively
coarser than in nature. The finer stria- tion may be at right or at oblique angles (probably also parallel) to the coarser
striation. The finer striation is most
evident in blue or purplish parts of
scales, altho it exists in other parts ; probably the darker background makes
it more plainly visible on blue portions. The finer striae appear to be formed of
rows of dots, but my objectives failed to determine this with certainty. The
finer striation is invisible on scales
treated with liquid reagents to remove
the air.
Both finer and coarser striation are
found on the under as well as the upper
side of the scales. At the edges of the
scales the coarser striation curves and
appears upon the transparent border of
the scales, the finer striation (see fig. I I, e) curves to meet the margins of
compartments ; the coarser striation is
evidently an external, longitudinal plica- tion of the scale-membrane, limited in
extent by the size of the scale itself, the finer striation is a plication or figuration of the inner side of the scale-membrane, limited in extent by the outline of the
compartment to which it belongs.
(To be continued.)




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