_Insect Pins._--In mounting insects for the cabinet, expressly made
entomological pins should be used. These come from three different
sources: Klaeger pins, made by Hermann Klaeger, Berlin, Germany; Karlsbad
pins, made by one or several firms in Karlsbad, Bohemia, Austria; and
Vienna pins, made by Miller, Vienna, Austria.[4] These three kinds of
pins have each their own slight advantages and disadvantages, so that it
is difficult to say which is the best. All have the disadvantage that
the pinned specimens are liable to be ruined by verdigris, and to
obviate this japanned ("black") insect pins are made by Klaeger and
Miller. These black pins are, however, much softer than the "white"
pins, and therefore more difficult to handle. A pin of 35 millimeters in
length will be found most convenient for pinning all insects excepting
the larger Lepidoptera and other heavy-bodied insects, for which a
longer pin may advantageously be used. According to the different
degrees of fineness, the pins are numbered from No. 00 (the finest in
the trade) to No. 7 or 8, but the numbers used by the different
manufacturers do not correspond with each other. In experience, pins of
Nos. 1, 2, 3, and 4 (Klaeger numbers) are more often needed than the
others. The long pins of the finer numbers (Nos. 0 and 00) are difficult
to handle in the collection and, for this reason, not to be recommended.
[4] In North America, Klaeger pins and Karlsbad pins can be obtained
through Mr. John Ackhurst, 78 Ashland Place, Brooklyn, N. Y., and
possibly also through Messrs. Blake & Co., 55 North Seventh street,
Philadelphia, Pa. The Vienna pins and the Minutien-Nadeln have to be
ordered direct through the manufacturer, Mr. Miller.
For many small insects, especially Microlepidoptera and Microdiptera,
which _must_ be pinned, even the finest ordinary insect-pins are too
large, and two special makes of pins are in use for this purpose. The
"elbow pin" (formerly made and sold by Dr. Kuenow, of Koenigsberg,
Prussia, Germany) consists of a piece of fine silver wire, pointed at
one end, and with a coil loop at the other end, into which a longer pin
(No. 3 or No. 4) is thrust. This pin is illustrated in Fig. 94. Still
more satisfactory are the "Minutien-Nadeln" (pins for minute insects)
manufactured by Mr. Miller, of Vienna, Austria, and which consist of a
straight piece (about 14 mm. long) of extremely fine steel wire which is
pointed at one end, and which is used in connection with a piece of
pith or cork. The mode of using this pin is shown in Fig. 101. These
fine and elbow pins may be obtained either "white" or japanned.
[Illustration: FIG. 94.--Insect mounted on "elbow-pin."]
"Many English entomologists use short pins, very much like those of
ordinary make, and my late friend Walsh never gave up the custom, and
most vehemently opposed the use of what he ridiculed as 'long German
skewers.' But the only advantage that can possibly be claimed for the
short pins is that they are less apt to bend, consequently more easily
stuck into the bottoms of boxes, and require less room; while, compared
with the long pins, they have numerous disadvantages. Long pins admit of
the very important advantage of attaching notes and labels to the
specimen; render it more secure from injury when handled, and from
museum pests in the cabinet; and on them several rows of carded
duplicates may be fastened, one under the other, so as to economize
room."
I have seen few old collections in better condition than that of the
late E. Mulsant, of Lyons, France; and he used iron wire, cut
slantingly, of the requisite length--a common custom in France. These
wires bend so easily and have such dull points that they require much
more careful manipulation than the pins, and the claim made for them
that they do not verdigris would, perhaps, be offset by their rusting in
moist climates or near the sea. Silver wire or silver-plated wire is
also used.
_Preparation of Specimens._--Upon the return from an excursion the
specimens should be prepared for the collection as soon as practicable.
If they have been collected in the forenoon they should be mounted the
same evening, and those collected during an afternoon or evening
excursion should be mounted the following morning, or, at any rate,
before they get dry and brittle. Even specimens collected in alcohol
should be attended to as soon as possible.
Specimens are taken from the collecting bottle, spread out on a sheet of
white blotting paper and cleaned from adhering impurities either with a
soft dry brush, or, in the case of species with hard covering, by
washing them with chloroform or ether or benzine where necessary.
Theoretically the best way of mounting would be to pin all specimens,
since the under side with its important characters then remains free for
examination. Pins adapted for pinning even the smallest insects have
been described above, but this pinning is such a delicate operation and
requires so much time that considering the large number of small
specimens that may be collected on a single short excursion it is next
to impossible to carry out this method, and therefore only the larger
specimens need be pinned and the smaller may be glued onto the paper
points described later. If the work is done with proper care all
insects can be prepared for the cabinet so that both the upper and under
surface of the specimen may be examined without further manipulation.
_Pinning._--"Insects should be pinned through the middle of the thorax,
when, as is more generally the case, this portion (the mesothorax) is
largely developed. Beetles (_Coleoptera_) and Bugs (_Hemiptera_),
should, however, be pinned, the former through the right elytron or
wing-cover (Fig. 95), and the latter through the scutel or triangular
piece behind the thorax, the pin issuing between the middle and hind
legs (Fig. 96). The specimens look very pretty with all the legs neatly
spread out, but for practical purposes it is better to let them dry in
the natural, partly bent position. It is a saving of time and space, and
the limbs are not so apt to break. The legs must also not reach too far
downward or they will interfere with the proper labeling and the secure
pinning of the specimen in the cabinet. Moreover, the antennae and legs
must be brought into such position that they will not obstruct the view
of any important part of the undersurface. The pin should always project
about half an inch above the insect to facilitate handling, and
uniformity in this regard will have much to do with the neat appearance
of the collection. In pinning very large and heavy insects on a No. 4 or
No. 5 pin, it is a good plan to first flatten the pin by a few blows of
a hammer, in order to prevent the specimen from subsequently turning
round on the pin."
[Illustration: FIG. 95.--Method of pinning and labeling Coleoptera
(original).]
In pinning specimens which have a flat or nearly flat undersurface and
short legs (as in many Coleoptera and Hemiptera and some Hymenoptera,
_e. g._ the Saw-flies) the specimens are laid on a piece of cork and
held in place there with the fingers or with a forceps. The pin is then
pushed through the insect at the proper point, care being taken not to
strike one of the legs or coxae, and that the pin passes through the
specimen in a vertical direction.
[Illustration: FIG. 96.--Method of pinning Hemiptera (original).]
After the pin has been pushed through the specimen it is taken out of
the cork and the specimen is pushed up to its proper height. This can be
done either by holding the specimen between the fingers or by placing it
on the upper edge of a thick book. A piece of cardboard provided with a
small hole may also be used for this purpose. The perforations in
ordinary sheet-cork, or the lapel of one's coat, will answer the same
purpose. In pinning Lepidoptera or Hymenoptera the specimen should lie
lightly in the angle formed by the thumb and first two fingers of the
left hand and the pin be carefully thrust through at the proper angle.
In pinning all insects the pin should be so inserted that the insect is
nearly at right angles with the pin, the posterior end being slightly
depressed.
_Mounting on Points._--Most insects which are too small to be pinned on
a No. 2 pin may be fastened to cardboard by means of gum tragacanth, gum
shellac, or any good glue. It is not always easy to determine whether to
pin a medium specimen or to glue it to a triangle. Pinned specimens are
more secure, and not so apt to fall or be knocked off, but they are
liable to become corroded by verdigris and ultimately lost, especially
in families the larvae of which are endophytous or internal feeders. It
is better to glue wherever there is doubt. A drop of corrosive sublimate
added to the water in which the gum tragacanth is dissolved will
indefinitely prevent its souring, but should not be used where the gum
is to come in contact with the pin, as it inclines the latter to
verdigris. In such cases a little spirits of camphor mixed with the gum
tragacanth is best. Shellac should be dissolved in alcohol and this
requires some time. This glue is not affected by moisture, and if it is
desired to remove the specimens, they must be immersed in alcohol until
the shellac is again dissolved.
A number of different kinds of glue are used by entomologists. The
requirements of a good glue are that it be colorless, and, what is of
greater importance, that the specimens adhere firmly to the paper points
so that there is little or no danger of their being jarred off. Those
glues which are readily soluble in cold or lukewarm water are perhaps
more convenient than those which require alcohol or chloroform for
dissolving. Gum arabic and gum tragacanth have the disadvantage that
they are more liable to attract mites and are more brittle, so that they
do not hold specimens as well as some of the liquid glues that are on
the market. Spalding's glue answers a very good purpose, as also the
preparation known to European entomologists as Leprieur's gum. White
bleached shellac, while requiring alcohol to dissolve it, has the
advantage that a very minute quantity suffices. In olden times the
method employed was simply to glue the specimen by the ventral side to
the middle of a quadrangular piece of cardboard, which was then pinned
on a No. 3 or No. 4 insect pin. This method is still in vogue with
English entomologists, but can not be recommended except for mounting
duplicates. Much better are the small isosceles triangles which, before
mounting the specimen, are pinned through near the base on a No. 2 or
No. 3 insect pin. Only the best and finest cardboard should be used for
this purpose, since that of poor quality is liable to be broken while
passing the pin through it and will yellow with age. "Reynolds's
Superfine Board," which may be ordered through any dealer in artist's
supplies of Devoe & Co., Fulton street, New York City, is perhaps the
best for this purpose. Some of the neatest mounting which I have had
done by any of my agents or assistants is by Mr. Albert Koebele, who
has used mica or gelatine instead of cardboard, the object being not
only to show the whole of the under side of the specimen, but to obscure
less of the light from the labels and to render the triangles less
conspicuous in the cabinet. These have been in use in the museum
collection only for the last two or three years, and whether they will
eventually tend to corrode the pins is not yet settled. Mica and
isinglass are also used for the same purpose. The points used in
mounting may easily be cut by hand to a convenient size, say one-fourth
of an inch (6-8 mm) long by one-sixteenth or less at the base, and
tapering to a point. The point may be narrower or wider to accommodate
insects of different sizes.
For cutting these triangles or points, various forms of punches similar
to the appended figure (Fig. 97) known to the trade as conductor's
punches may be used, and points thus cut are to be preferred to those
made by other means, on account of the greater uniformity secured.
An experienced hand, however, will cut these points very rapidly and
accurately with a pair of shears, and most collectors use no special
instrument for this purpose.
The punches mentioned may be obtained of the manufacturers[5] of such
instruments at from $2 to $3. Care should be observed in ordering to
state explicitly the length, width at base and point, or, what is
better, to inclose sample of the size of point it is desired to cut; but
above all, to state that the block of paper to be cut out is the result
desired, and that the instrument should cut clean and even, with no
ragged edges.
[5] Montgomery & Co., 105 Fulton street, New York City.
[Illustration: FIG. 97.--Insect punch for cutting triangles or points
(original).]
For mounting different forms and sizes the fastidious collector uses
four or five sizes of points, but for all practical purposes one to cut
a card point not less than 1.3 mm at the base and prolonged as nearly as
possible to a point, and another a trifle wider at the base, say 11/2 or 1
2/3 mm and with a point about 11/2 mm in width will suffice.
[Illustration: FIG. 98.--Points for mounting insects (original).]
For mounting most long-bodied insects, _e. g._, Staphylinidae and
Elateridae, an oblong card say 11/2 mm in width is desirable. With a little
care these may be cut with sufficient uniformity with scissors. Seven
and one-half millimeters may be taken as a standard of length, as this
is about the size used by the majority of our best collectors. Shorter
points, say 6 mm or one-quarter inch long, are sometimes preferred,
where economy of space is a desideratum.
A series of four points of different sizes for mounting insects is shown
in the accompanying illustration. The sharp-pointed one, _a_, is
designed for the minutest forms and the larger points for large insects.
The largest should be mounted on points of a nearly rectangular shape,
shown at _d_. The dimensions of these points as adopted by most
entomologists, are as follows:--
+------+---------+----------+--------+
| | Length. | Breadth. | Point. |
+------+---------+----------+--------+
| _a_ | 7.5mm. | 1.5mm. | .0mm. |
| _b_ | 7.5 | 1.5 | .4 |
| _c_ | 7.5 | 1.5 | .6 |
| _d_ | 7.5 | 1.6 | 1.6 |
+------+---------+----------+--------+
The point or triangle should be mounted on the pin and directed to the
left, the height from the top of the pin varying somewhat with the
specimen, but averaging about one-half an inch. The insect is then glued
to the point with the head pointed forward. In the case of Coleoptera
and Hymenoptera, and in fact of most insects, the specimen is mounted
with the back uppermost, but in the case of the smaller Hymenoptera it
is advisable to mount some of the specimens, at least, on the left side
(see Fig. 99). This directs the legs toward the pin, as a matter of
safety, prevents their being broken in handling, and also gives
opportunity for subsequent examination of the back, side, and venter of
the specimen. Coleopterists always mount specimens on the venter, and in
the case of a correctly mounted specimen the whole underside of the body
should be available for examination except the right half of the
metasternum, as shown in figure 100.
[Illustration: FIG. 99.--Insect mounted on cardboard triangle.]
[Illustration: FIG. 100.--Method of gluing beetle on paper point
(original).]
In mounting minute insects a few precautions are necessary. The beginner
usually uses too much glue or shellac, and the result is that the
mounted specimens are more or less covered with the fluid, so as to
render them unfit for examination. If, on the other hand, too little of
the glue is used, the specimens are not securely fastened to the paper
point, and are liable to be jolted off by the slightest jar. Before
mounting specimens the legs and antennae must be brought into the proper
position by means of a brush or with a dissecting needle, so that they
may easily be seen. A supply of paper points should always be at hand,
and after selecting one of the proper size for the specimen, with an
acute tip for a very small specimen and with a more obtuse point for a
larger one, a small quantity of glue is applied to the tip by means of a
pointed stick, such as a toothpick, the amount varying with the size of
the specimen. The tip of a moistened brush may be used to transfer the
specimen to the point, or one will soon become dextrous enough to do
this without the aid of the brush. The specimens are then allowed to dry
in a horizontally placed box. If the drying box is placed in a vertical
position the specimens, especially long-bodied ones, are liable to
topple over before the glue has become firm.
[Illustration: FIG. 101.--Cecidomyiid mounted on pith (original).]
Delicate flies and Microlepidoptera, which it will not do to fasten with
mucilage, may first be mounted on the fine pins described above and
these thrust into oblong or triangular bits of pith or cork, which are
mounted on larger pins as shown in Figures 101 and 102. This affords a
very satisfactory method of mounting, particularly as the different
sexes may be brought together on the same bit of pith, or the adult and
puparium in Diptera, as shown at Figure 101. Strips of stout cardboard
with the pins run through the narrow edge may also be used. The method
of mounting minute Hymenoptera and Diptera and other insects on a bent
wire, mentioned above, is illustrated at Figure 94. This method has not
proved so satisfactory, as the wires are apt to become loose on the pin.
[Illustration: FIG. 102.--Microlepidoptera mounted on pith (original).]
[Illustration: FIG. 103.--Method of mounting duplicates (original).]
_Mounting Duplicates._--If the collector finds more specimens of a rare
species than he cares to have in his collection, the excess may be
mounted as duplicates. If the species happens to be of a large size the
specimens are pinned in the ordinary way, but if small enough to be
gummed, there is a most convenient method of rapidly mounting the
specimens so that they may be sent through the mail with much less risk
of getting broken or knocked off than if glued on paper points, and will
also take up very little room in the duplicate boxes. It consists in
gluing the specimens in a transverse row on a strip of white card paper
with one of the glues soluble in water, care being taken that between
the individual specimens some space be left, and further that the heads
and antennae do not project beyond the edge of the paper. The width of
the paper strip must be somewhat greater than the length of the
specimen, so that below the latter there is sufficient room for
inserting a pin through the paper. After the glue has become dry the row
of specimens is cut with scissors into several smaller rows of
convenient size, so that on each of these rows there are two or three or
more specimens, according to the size of the species. A locality label
is pushed high up on a No. 3 or No. 4 pin, and one of the mounted rows
of specimens is then pinned and pushed up near the locality label; a
second row is then pinned and pushed near the first row, and the same
process continued with the third row and so on. A single pin will thus
bear five or six rows, and in giving away or sending away specimens the
lowest row is taken from the pin and repinned for mailing. The
accompanying figure (Fig. 103) illustrates the mounting of a
moderate-sized species in rows of two specimens each. This method of
mounting duplicates may be adopted not only for Coleoptera, but also for
Heteroptera, Homoptera (excepting Aphididae and allied families), smaller
Orthoptera, and Hymenoptera. It is, however, impracticable for
Lepidoptera, Diptera, and most Neuroptera.
_Temporary Storage of Specimens._--If the entomologist is prevented from
mounting his captures soon after returning from an expedition, or if, on
extended collecting trips, time does not offer for this purpose,
specimens of almost all orders except the Lepidoptera, Orthoptera, and
Neuroptera may be placed in a small, tightly closing pill box, care
being taken to keep the larger specimens apart from the small ones. In
this way specimens will keep for an indefinite period, provided they are
properly packed. In the case of the traveling collector, where the
material is to be carried from point to point at great risk of breaking,
specimens should be packed very carefully to prevent any shaking or
rattling about in the boxes. This may be done by placing a round piece
of soft paper on the top of the specimens in the pill box. This paper
should be gently pressed down and the empty space above filled with
other layers of paper or with cotton. The packing of specimens between
cotton is not recommended, as it is a difficult and tedious task to
afterwards free them from the adhering fibers. Layers of soft paper or,
yet better, velvet, are preferable.
[Illustration: FIG. 104.--Method of preserving Diurnal Lepidoptera in
paper envelopes. (After Kiesenwetter.)]
_Envelopes for Lepidoptera, etc._--On an extended trip, it will be found
impracticable to mount and prepare insects requiring cumbersome
apparatus for spreading, as Lepidoptera or Neuroptera, and a very
excellent plan consists in folding the wings of the insect so that the
lower surfaces come together and then placing it in a triangular
envelope, as shown in the accompanying illustration. The collector
should be provided with a quantity of paper of the requisite dimensions
for making these envelopes, and specimens, as they are taken from the
collecting bottle, may be rapidly inclosed in them, labeled, and packed
away in a tight wooden (not tin) box containing a supply of naphthaline,
the specimens thus occupying the minimum of space. Specimens secured in
this way may be kept without further manipulation indefinitely or until
time is found to relax and set them. This is also an excellent method
of sending diurnal Lepidoptera and Dragon-flies through the mails and is
preferable in some respects to mailing spread specimens.
[Illustration: FIG. 105.--Spreading board for Lepidoptera.]
[Illustration: FIG. 106.--Needle for spreading insects.]
_Directions for Spreading Insects._--"For the proper spreading of
insects with broad and flattened wings, such as butterflies and moths, a
spreading board or stretcher is necessary. One that is simple and
answers every purpose is shown at Fig. 105. It may be made of two pieces
of thin whitewood or pine board, fastened together by braces at the
ends, but left wide enough apart to admit the bodies of the insects to
be spread; strips of cork or pith, in which to fasten the pins, may then
be tacked or glued below so as to cover the intervening space. The
braces must be deep enough to prevent the pins from touching anything
the stretcher may be laid on, and by attaching a ring or loop to one of
them the stretcher may be hung against a wall, out of the way. For
ordinary-sized specimens I use boards 2 feet long, 3 inches wide, and
1/3 inch thick, with three braces (one in the middle and one at each
end) 11/2 inches deep at the ends, but narrowing from each end to 1 1/6
inches at the middle. This slight rising from the middle is to
counteract the tendency of the wings, however well dried, to drop a
little after the insect is placed in the cabinet. The wings are held in
position by means of strips of paper (Fig. 105) until dry. For
stretching the wings and for many other purposes, a handled needle will
be found useful. Split off, with the grain, a piece of pine wood 3 or 4
inches long; hold it in the right hand; take a medium-sized needle in
the left hand; hold it upright with the point touching a walnut table,
or other hard-grained wood, and bring a steady pressure to bear on the
pine. The head of the needle will sink to any required distance into the
pine, which may then be whittled off, and you have just the thing you
want (Fig. 106). To obtain uniformity in the position of the wings, a
good rule is to have the inner margins of the front wings as nearly as
possible on a straight line. When the specimens are thoroughly stiff and
dry, they should be taken from the stretcher and kept for several weeks
in the drying box before being permanently placed in the cabinet. The
drying box is simply a box of any required dimensions, containing a
series of shelves on which to pin the specimens, and without a solid
back or front. The back is covered on the inside with fine gauze and on
the outside with coarser wire, and the door in front consists of a
close-fitting frame of the same material, the object being to allow free
passage of air, but at the same time to keep out dust and prevent the
gnawings of mice and other animals. The shelves should be not less than
2 inches deep, and if made in the form of a quadrangular frame, braced
with two cross-pieces on which to tack sheet cork, they will serve for
the double purpose of drying spread specimens and for the spreading of
others, as there are many insects with long legs which are more
conveniently spread on such a board, by means of triangular pieces of
stiff cardboard braces or 'saddles,' than on the stretcher already
described. Two of these braces are fixed on the setting board, by means
of stout pins, at sufficient distances apart to receive the body between
them. The wings are then spread upon them and kept in place until dry by
means of additional braces. In the case of bees, wasps, etc., the pin
may be thrust well into the cork or pith so that the wings may be
arranged in the proper position and braced and supported by strips of
stout cardboard. This method is especially recommended in the case of
the Fossorial wasps, the legs of which, if mounted in an ordinary
spreading board, can not be properly arranged.
In spreading Lepidoptera I have used, in the place of a number of paper
strips pinned across the wings, blocks of glass of various sizes to hold
the wings in position. My method of mounting, with a large amount of
material on hand to be attended to, consists in pinning a row on the
spreading-board and fixing the wings in position with spreading needles,
fastening them with a single narrow strip of paper placed next the body.
The entire spreading-board is filled with specimens in this way, a
single long strip of paper on either side answering to keep the wings of
all the specimens in position. Then, instead of pinning additional
strips to hold the wings flat and securely in position, the pieces of
glass referred to are used, placing them on the wings of the insect.
With the use of glass the spreading-board must always be kept in a
horizontal position and must never be disturbed. The advantage of the
glass is that the wings can be seen through it and more truly adjusted.
Spreading-boards may be made as described above, or it may be of
advantage, when a good deal of work is to be done, to adopt a somewhat
different method. Five or six spreading-boards may be made together,
forming a sort of shelf. A number of these shelves may be constructed
and the whole combined in a case with a screen cover to exclude insects.
The individual shelves may be arranged with grooves to slide on tongues
in the side of the case. A screen-covered case for spreading-boards is
always desirable, as the insects are otherwise very liable to be eaten
by roaches or other insects. A spreading-case of the form described is
shown at Fig. 107.
_A new Apparatus for Spreading Microlepidoptera._--For the spreading of
Microlepidoptera my assistant, Mr. Theo. Pergande, has devised an
apparatus, represented in the accompanying illustration, which he finds
very convenient. It consists of a small spreading-block represented at
_B_ and the support with attachment shown at _A_. The former is made in
a long strip of the shape shown in the illustration, having a square
groove, _c_, cut in the top. Over this is glued a thin strip of wood,
_b_, say 1/8 inch thick, and a narrow slit is sawed in the center of
this above, cutting through into the groove _c_. This is then sawed up
into pieces of uniform length, say 11/2 to 2 inches, and the block is
completed by the insertion of a rectangular strip of pith or cork into
the groove. The Micro is pinned on a short black pin, and the pin is
thrust down into the narrow opening made by the saw and is held firmly
by the pith or cork. This block is then slid into the groove in the
setting-board _A_, which narrows slightly from _e_, and pushed along
until firmly secured (_d_). The operator can then rest his hands and
arms on either side of the support, and, if necessary, bring a large
hand lens over the object by means of a support with ball-and-socket
joint shown at _e_. The wings may thus be easily and accurately arranged
and fixed in position with pins or strips of paper, as in the ordinary
mounting of such insects. Two or three specimens may be mounted on each
of these blocks. The construction of the support is indicated in the
annexed drawing. One side is attached by clamps, shown enlarged at
_f_, which afford means of adjusting the width of the slit in which the
small sawed blocks slide and correct the shrinking or swelling which may
take place in moist or dry seasons. The advantage of the apparatus is
that the operator has the setting block firmly fixed before him and
has both hands free to manipulate the wings of the insect in addition to
having the lens in a convenient position, the use of which is necessary
in the preparation of the very minute forms.
[Illustration: FIG. 107.--Spreading-case (original).]
[Illustration: FIG. 108.--Spreading apparatus for Microlepidoptera
(original).]
_Spreading Microlepidoptera._--The mounting of Microlepidoptera is about
the most delicate work in entomotaxy, and I can not do better than
quote the explicit directions given by Lord Walsingham on the subject.
Returning to camp I put a few drops of liquid ammonia on a small piece
of sponge and place it in a tin canister with such of the boxes as do
not contain the smallest species, and put these and the remainder away
until morning in a cool place. In the morning I prepare for work by
getting out a pair of scissors, a pair of forceps, my drying-box
containing setting-boards, a sheet of white paper, and some pins.
First, I cut two or three narrow pieces of paper from 3 to 6 lines wide,
or rather wider, according to the size of the largest and smallest
specimens I have to set. I then double each of these strips and cut it
up into braces by a number of oblique cuts. Now I turn out the contents
of the canister and damp the sponge with a few drops of fresh ammonia,
refilling with boxes containing live insects. Those which have been
taken out will be found to be all dead and in a beautifully relaxed
condition for setting. Had the smallest specimens been placed in the
canister over night there would have been some fear of their drying up,
owing to the small amount of moisture in their bodies.
If the weather is very hot there is some danger of killed insects
becoming stiff while others are being set, in which case it is better to
pin at once into a damp cork box all that have been taken out of the
canister, but under ordinary circumstances I prefer to pin them one by
one as I set them.
Taking the lid off a box, and taking the box between the finger and
thumb of the right hand, I roll out the insect on the top of the left
thumb, supporting it with the top of the forefinger and so manipulating
it as to bring the head pointing toward my right hand and the thorax
uppermost. Now I take a pin in the right hand and resting the first
joint of the middle finger of the right against the projecting point of
the middle finger of the left hand to avoid unsteadiness, I pin the
insect obliquely through the thickest part of the thorax, so that the
head of the pin leans very slightly forward over the head of the insect.
After passing the pin far enough through to bring about one-fourth of an
inch out below,[6] I pin the insect into the middle of the groove of a
setting board so that the edge of the groove will just support the under
sides of the wings close up to the body when they are raised upon it.
The board should be chosen of such a size as will permit of the
extension of the wings nearly to its outer edge. The position of the pin
should still be slanting a little forward. The wings should now be
raised into the position in which they are intended to rest, with
especial care in doing so not to remove any scales from the surface or
cilia of the wings. Each wing should be fastened with a brace long
enough to extend across both, the braces being pinned at the thick end,
so that the head of the pin slopes away from the point of the brace;
this causes the braces to press more firmly down on the wing when fixed.
The insect should be braced thus: The two braces next the body should
have the points upwards, the two outer ones pointing downwards and
slightly inwards towards the body, and covering the main portion of the
wings beyond the middle. Antennae should be carefully laid back above the
wings, and braces should lie flat, exercising an even pressure at all
points of their surface. The fore wings should slope slightly forwards
so that a line drawn from the point of one to the point of the other
will just miss the head and palpi. The hind wings should be close up,
leaving no intervening space, but just showing the upper angle of the
wing evenly on each side. I can give no more precise directions as to
how this desirable result may most simply and speedily be attained; no
two people set alike. Speed is an object; for I have often had to set
twelve dozen insects before breakfast. A simple process is essential,
for a man who is always pinning and moving pins, and rearranging wings
and legs, is sure to remove a certain number of scales and spoil the
appearance of the insect, besides utterly destroying its value. I raise
each of the fore wings with a pin, and fix the pin against the inner
margin so as to keep them in position while I apply the braces. Half the
battle is really in the pinning. When an insect is pinned through the
exact center of the thorax, with the pin properly sloped forward, the
body appears to fall naturally into its position on the setting board,
and the muscles of the wings being left free are easily directed and
secured; but if the pin is not put exactly in the middle it interferes
with the play of the wings. Legs must be placed close against the body
or they will project and interfere with the set of the wings. Practice,
care, and a steady hand will succeed. When all the insects that have
been killed are set the contents of the canister will be found again
ready, twenty minutes being amply sufficient to expose to the fumes of
ammonia. Very bright green or pale pink insects should be killed by some
other process, say chloroform, as ammonia will affect their colors.
[6] This applies to the use of short pins, which should subsequently be
connected through strips of pith with longer pins. For some of the
larger micros the long pins may be used directly and a different
spreading board employed.
Insects should be left on the setting boards a full week to dry; then
the braces may be carefully removed and they may be transferred to the
store box.
In my own experience I have found that a touch or two of the chloroform
brush on the pill-box containing small moths is sufficient to either
kill or so asphyxiate them that they can easily be mounted. I have also
found that strips of corn pith or even of soft cork, with grooves cut
into them, are very handy for the pinning and spreading, and that by
means of a small, broad-tipped, and pliable forceps the smallest
specimens can be deftly arranged in the groove and kept in place until
pinned. In fact, for all persons who have not very great experience and
dexterity this method is perhaps more to be recommended than that of
holding them between the thumb and fingers. Where chloroform is used
either to kill or deaden specimens, it is important that after they are
once spread and in the drying box they should be subjected to an
additional asphyxiation, as the larger species may revive and are apt to
pull away from the holding strips, and thus rub off their scales.
Microlepidoptera, together with Microhymenoptera and Diptera may be
conveniently pinned on fine, short pins, and these thrust into an oblong
bit of cork or pith. This form of mounting has already been described
and is represented in figure 102. The neatest mounting of
Microlepidoptera which I have seen is the work of my assistant, Mr.
Albert Koebele, who mounts these insects on an oblong strip of pith.
This is very light and presents no difficulty in pinning. The strips may
be made of considerable length and both sexes may be pinned on the same
block (see Fig. 103). Most Lepidoptera present on the under surface an
entirely different aspect from that on the upper surface, and, in such
cases, it is a good plan to mount a number of specimens obversely.
_Relaxing._--It will frequently be desirable to re-spread insects which
have been incorrectly mounted, or to spread specimens which have been
collected and stored in papers, or pinned and allowed to dry without
being prepared for the cabinet. Such specimens may be relaxed by placing
them in a tight tin vessel half filled with moist sand to which a little
carbolic acid has been added to prevent molding. Small specimens will be
sufficiently relaxed to spread in twenty-four hours. Larger specimens
require from two to three days. More rapid relaxing may be caused by the
use of steam, and a flat piece of cork with the specimens laid or pinned
thereon and floated on the top of hot water in a closed vessel
constitutes an excellent relaxing arrangement.
_Inflation of the Larvae of Lepidoptera._--The larvae of Lepidoptera
preserved in alcohol are excellent for anatomical and general study, but
are not very suitable for use in economic displays. This means of
preservation also has the disadvantage of not generally preserving the
natural color and appearance of the specimens. These objections may be
avoided, however, by the dry method of preserving larvae, viz, by blowing
or inflation. The process may be described as follows: The larva may be
operated upon alive, but should preferably be first killed by dipping in
chloroform or alcohol, or in the cyanide bottle. It is then placed on a
piece of blotting paper and the alimentary canal caused to protrude from
one-eighth to one-fourth of an inch, by rolling a pencil over the larva
from the head to the posterior extremity. The protruding tip is then
severed with a sharp knife or pair of dissecting scissors, and the
contents of the abdomen are forced out by passing a pencil, as before, a
number of times over the larva. Great care should be exercised in
expressing the fluids not to press the pencil too strongly against the
larva or to continue the operation too long, as this will, especially in
delicate larvae, remove the pigment from the skin, and the specimen when
dried will show discolored spots and be more or less distorted. The
larva should be moved from place to place on the blotting paper during
the operation, so as not to become soiled by its own juices. A straw, or
a glass tube drawn to a point at the tip, is then inserted in the
protruding portion of the alimentary canal. If a straw is used the larva
may be fastened to it by thrusting a pin through the wall of the canal
and the straw. In the case of the glass tube the alimentary canal can be
caused to adhere by drying for a few minutes and this operation may be
hastened and the fastening made more secure by touching the point of
union with a drop of glue. The straw or glass tube is then attached to a
small rubber bag, previously inflated with air, the ordinary dentist's
or chemist's gas bag answering admirably for this purpose. The larva is
now ready for drying, and for this purpose a drying oven is required
into which it is thrust and manipulated by turning it from side to side,
to keep it in proper shape and dry it uniformly until the moisture has
been thoroughly expelled. An apparatus which I have found very
convenient for this purpose is represented at Fig. 109. It consists of a
tin box with mica or glass slides, _e_, to allow the larva to be
constantly in sight. It has also a hinged top, _b_, which may be kept
closed or partly open, or entirely open, as may be necessary, during the
operation. The ends of the box are prolonged downward about 5 inches,
forming supports for it, _g_. Beneath it is placed an alcohol lamp, _f_,
which furnishes the heat. In the end of the box is a circular opening,
_d_, for the introduction of the larva, and this may be entirely or
partly closed by a sliding door, _a_. It will be found of advantage to
line the bottom of the box (inside) with a brass screen of very fine
mesh to distribute and equalize the heat. This apparatus can be very
easily made by any tinsmith and will answer every purpose.
[Illustration: FIG. 109.--Drying oven for the inflation of larvae
(original).]
The larvae of Microlepidoptera or young larvae may be dried without
expressing the body contents, and will keep, to a great extent, their
normal shape and appearance. The method consists in placing them on a
sand bath, heated by an alcohol lamp. The vapor generated by the heat in
the larvae inflates them and keeps the skin taut until the juices are
entirely evaporated. They may then be glued at once to cardboard and
pinned in the cases.
In the mounting of large inflated larvae I have adopted the plan of
supporting them on covered copper wire of a size varying with the size
of the larva. A pin is first thrust through a square bit of cork and the
wire brought tightly about it and wrapped once or twice, compressing the
cork and giving a firm attachment to the pin. The wire is then neatly
bent to form a diamond-shaped loop about one-sixth of an inch in length
and again twisted loosely to the end--the length of the twisted portion
about equalling that of the larva to be mounted. This is then either
thrust into the blown skin of the larva through the anal opening, the
larva being glued to the wire by the posterior extremity, or the larva
is glued to the wire by the abdominal legs and venter, thus resting on
the wire as on a twig. This style of mounting is illustrated in Pl. I.
With a little experience the operator will soon be able to inflate the
most delicate larvae and also the very hairy forms, as for instance
_Orgyia leucostigma_, without the least injury, so that the natural
colors and appearance will be preserved.
Another very good method, and still safer, is to blow with straw, cut
the straw square off at the anus, and then preserve the thoroughly dried
and blown specimen in a glass tube of about the same length and diameter
as the larva. This arrangement in conjunction with the tube holder,
which will be described further on, is one of the most satisfactory for
the preservation of inflated larvae.
For the biological-display collection, larvae may be blown in various
natural positions, to be subsequently fastened on leaf or twig or in
burrows which they have occupied. Fastened to artificial foliage in
which nature is imitated as much as possible, such blown larvae are quite
effective.
_Stuffing Insects._--Large larvae may sometimes be satisfactorily
preserved for exhibition purposes by stuffing them with cotton. The
method consists simply in making a small slit with the dissecting
scissors or a short scalpel between the abdominal prolegs, and removing
the body contents. Powdered arsenic or some other preservative should be
put in the body of the larva with the cotton used in stuffing it, and
the slit closed by a few stitches, when the larva may be dried and
mounted on a twig or leaf. This method of stuffing with cotton is also
applicable in the case of certain large-bodied insects which, if mounted
and put away without preparation, would be liable to decompose, as, for
instance, the larger moths, grasshoppers, etc. A slit can be made in the
center of the abdomen or near the anus beneath, and the body contents
removed and replaced with cotton. Stuffing in this way with cotton is of
especial advantage in the case of certain of the large endophytous
insects which grease badly. The cut will not be noticed after the insect
has dried, or it may be closed by a stitch or two.
_Dry Preservation of Aphides and other soft-bodied Insects._--Difficulty
has always been experienced in preserving soft-bodied insects,
particularly Aphides, in a condition serviceable for subsequent
scientific study. Kept in alcohol or other antiseptic fluid, they almost
invariably lose much of their normal appearance, and many of the
important characteristics, especially of color, are obscured or lost.
The balsam mount is also unsatisfactory in many respects, as the body is
always more or less distorted and little can be relied upon except the
venation and the jointed appendages. A method of preserving soft-bodied
insects by means of the sudden application of intense heat was
communicated to the _Entomologische Nachrichten_, Vol. IV, page 155, by
Herr D. H. R. von Schlechtendal. It is claimed for this method that the
Aphides and other soft-bodied insects can be satisfactorily preserved in
form and coloring, the success of the method being vouched for by a
number of well-known German entomologists, Kaltenbach, Giebel,
Taschenberg, Mayr, and Rudow. A condensed translation of the method
employed by Schlechtendal is given by J. W. Douglas in the
_Entomologists' Monthly Magazine_ for December, 1878, which I quote:
The heat is derived from the flame of a spirit or petroleum lamp. Above
this is placed a piece of sheet-tin, and over this the roasting
proceeds. A bulging lamp cylinder, laid horizontally, serves as a
roasting oven. In this the insect to be dried, when prepared as
directed, and stuck on a piece of pith, is to be held over the flame; or
the cylinder may be closed at the lower end with a cork, which should
extend far inwards, and on this the insect should be fastened; the
latter mode being preferable because the heat is more concentrated, and
one hand is left free. The mode of procedure varies according to the
nature of the objects to be treated. For the class of larger objects,
such as Hemiptera, Cicadina, and Orthoptera, in their young stages of
existence, the heat must not be slight, but a little practice shows the
proper temperature required. If the heat be insufficient, a drying up
instead of a natural distention ensues. The insect to be roasted is to
be pierced by a piece of silver wire on the under side of the thorax,
but it is not to be inserted so far as to damage the upper side, and the
wire should then be carried through a disk of pith, placed beneath the
insect, on which the legs should be set out in the desired position. But
with some objects, such, for instance, as a young _Strachia_, the drying
proceeds very quickly, so that if distention be not observed then the
heat is too great, for the expansion of the air inside will force off
the head with a loud report; also, with softer, thicker Pentatomidae care
must be taken to begin with a heat only so strong that the internal
juices do not boil, for in such case the preparation would be spoiled.
It is of advantage to remove the cylinder from time to time, and test,
by means of a lens, if a contraction of the skin has taken place on any
part; if so, the roasting is to be continued. The desired hardness may
be tested with a bristle or wire. For _Aphides_ the _living Aphis_ is to
be put on a piece of white paper, and at the moment when it is in the
desired position it is to be held over the flame, and in an instant it
will be dead and will retain the attitude. Then put it, still on the
paper, into the oven; or, still better, hold it over the heated tin,
carefully watching the drying and moving the paper about in order to
prevent it getting singed. The roasting is quickly accomplished in
either way, but somewhat slower out of the oven especially in the larger
kinds, such as Lachnus. If the paper turn brown it is a sure sign that
caution is requisite. To pierce these brittle preparations for
preservation is hazardous, and it is a better way to mount them with gum
on card, placing some examples on their back.
For Cecidomyidae, Agromyzidae, Cynipidae, and other small insects liable to
shrink, yet containing but little moisture, such as Poduridae,
Pediculidae, Psyllidae, etc., another method is adopted. Over the insect,
mounted on a wire, etc., as above directed, a thin chemical reagent
glass or glass rod, heated strongly at one end, is held, and the heat
involved is generally sufficient to bring about the immediate drying and
distention, but if the heat be too little the process must be repeated;
and, although by this method the danger of burning is not obviated, yet
the position of the legs is maintained much better than by the aforesaid
roasting.
Larvae of all kinds, up to the size of that of _Astynomus aedilis_, even
when they have long been kept in spirits, may be treated successfully by
the roasting method; but with these objects care must be taken that the
heat is not too strong or else the form will be distorted. For small
larvae it is preferable to use a short glass, in order better to effect
their removal without touching the upper part, which becomes covered
with steam, and contact with which would cause the destruction of the
preparation. Larvae of Coleoptera, which contain much moisture or have a
mucous surface, must lie on a bed of paper or pith in order to prevent
adhesion and burning, and these may be further avoided if the cylinder
be slightly shaken during the process, and the position of the object be
thereby changed.
Many Aphides and Coccids are covered with a waxy secretion which
interferes very materially with their easy examination. Mr. Howard has
overcome this difficulty by the following treatment:
"With Aphides and Coccids which are covered with an abundant waxy
secretion which can not be readily brushed away, we have adopted the
plan of melting the wax. We place the insect on a bit of platinum foil
and pass it once over the flame of the alcohol lamp. The wax melts at a
surprisingly low temperature and leaves the insect perfectly clean for
study. This method is particularly of use in the removal of the waxy
cocoon of the pupae of male Coccidae, and is quicker and more thorough
than the use of any of the chemical wax solvents which we have tried."
(_Insect Life_, I, p. 152.)
_Mounting Specimens for the Microscope._--The study of the minuter forms
of insect life, including Parasites, Thysanura, Mallophaga, the newly
hatched of most insects, etc., requires the use of the microscope, and
some little knowledge of the essentials of preparing and mounting
specimens is needed. The subject of mounting the different organs of
insects and the preparation for histological study of the soft parts of
insects opens up the immense field of microscopy, the use of the
innumerable mounting media, the special treatment of the objects to be
mounted, staining, section-cutting, and many other like topics, a full
description of which is altogether out of place in the present work.
Anyone desiring to become thoroughly versed in the subject should
consult some of the larger manuals for the microscopist, of which there
are many. For the practical working entomologist, however, a knowledge
of all these methods and processes is not essential, and in my long
experience I have found that mounting in Canada balsam will answer for
almost every purpose. The softer-bodied forms will shrink more or less
in this substance, and it is frequently necessary to make studies or
drawings of them when freshly mounted; or, if additional specimens are
preserved in alcohol, they will supplement the mounted specimens and the
material may be worked up at the convenience of the student. The
materials for the balsam mounts may be obtained of any dealer in
microscopical supplies. They consist of glass slides, 3 inches by 1
inch, thin cover-glasses of different dimensions, and the prepared
balsam. The balsam is put up very conveniently for use in tin tubes. A
sufficient quantity is pressed out on the center of the glass slide,
which has previously been made thoroughly clean and dry, the insect is
removed from the alcohol, and when the excess of liquor has been removed
with bibulous paper, it is placed in the balsam, the limbs and antennae
being arranged as desired by the use of fine mounting-needles. A
cover-glass, also made thoroughly clean and dry, is then placed over the
specimen and pressed gently until the balsam entirely fills the space
between the cover and the glass slide. The slide should then be properly
labeled with a number referring to the notes on the insect, preferably
placed on the upper edge of the slide above the cover-glass, and also a
label giving the number of the slide and the number of the slide box. On
the opposite end of the slide may be placed the label giving the name of
the specimen mounted and the date. If a revolving slide table is
employed to center the mounts, the appearance of the slide may be
improved by adding a circle of asphalt or Brunswick black. With the
balsam mounts, however, this sealing is not necessary. The slide (Fig.
110) should then be placed in a slide case with the mount uppermost, and
should be kept in a horizontal position to prevent sliding of the
cover-glass and specimen until the balsam is thoroughly dried. For
storing slides I have found very convenient the box shown at Fig. 111.
It is constructed of strong pasteboard and is arranged for holding
twenty-six slides. The cover bears numbers from 1 to 26, opposite which
the name of each insect mounted, or the label on the slide, may be
written. This box when not in use is kept in a pasteboard case, on which
may be placed the number of the box. These slide cases may be stored in
drawers or on shelves made for the purpose. In mounting specimens taken
from alcohol it is advisable to put a drop of oil of cloves upon them,
which unites with the balsam and ultimately evaporates. The occurrence
of minute air bubbles under the cover-glass need occasion no uneasiness,
for these will disappear on the drying of the balsam.
[Illustration: FIG. 110.--Balsam mount, showing method of labeling, etc.
(original).]
[Illustration: FIG. 111.--Slide case, showing method of labeling case
and of numbering and labeling slides (original).]
In mounting minute Acarids or mites it has been found best to kill the
insects in hot water, which causes them to expand their legs, so that
when mounted these appendages can readily be studied. If mounted living,
the legs are almost invariably curled up under the body and can not be
seen. This method may also be used in the case of other minute insects.
Some insects, such as minute Diptera, are injured by the use of hot
water, and for these dipping in hot spirits is recommended.
In the mounting of Aphides the same difficulty is avoided in a measure
by Mr. G. B. Buckton, author of "A Monograph of the British Aphides," by
first placing a few dots of balsam on the glass slide, to which the
insect is transferred by means of a moistened camel's-hair brush. The
efforts of the insect to escape will cause it to spread out its legs in
a natural position and a cover glass may then be placed in position and
a drop of the balsam placed at the side, when, by capillarity, it will
fill the space between the slide and cover glass and the limbs will be
found to have remained extended. If three or four drops of the balsam
are put on the glass the wings may also be brought down and caught to
them so that they will remain expanded in shape for examination.
_Preparing and Mounting the Wings of Lepidoptera._--The student of
Lepidoptera will frequently find it necessary in the study of the
venation of wings to bleach them or denude them of their scales in some
way. Various methods of bleaching and mounting the wings of these
insects have been given, and a few of them may be briefly outlined.
The simplest and quickest, but perhaps the least satisfactory, method is
to remove the scales with a camel's-hair brush. This will answer for the
larger forms and where a very careful examination is not required. For
more careful examination and study the wings are first bleached by the
action of some caustic solution and then mounted in balsam for permanent
preservation. Chambers's method for Tineina, Tortricina, Pyralidina, and
the smaller moths generally, is as follows: The wing is placed on a
microscopic slide in from 3 to 4 drops of a strong solution of potash,
the amount varying according to the size of the wing. A cover of glass
is then placed in position on the wing as in ordinary mounting.
The quantity of liquid should be sufficient to fill the space beneath,
but not sufficient to float the cover glass. The mount is then placed
over an alcohol flame, removing it at the first sign of ebullition, when
the wing will be found denuded, if it be a fresh specimen. An old
specimen, or a larger wing, will require somewhat more prolonged
boiling. The fluid is drawn off by tilting the glass or with bibulous
paper, and the potash removed by washing with a few drops of water. The
cover glass is then removed and the wing mounted either on the same
slide in balsam or floated to another slide, or at once accurately
sketched with the camera lucida. Permanent mounting, however, is always
to be recommended.
The Dimmock method of bleaching the wings of Lepidoptera, given in
Psyche, Vol. I, pp. 97-99, is as follows: He uses for bleaching a
modification of the chlorine bleaching process commonly employed in
cotton bleacheries, the material for which is sold by druggists as
chlorate of lime. The wings are first soaked in pure alcohol to dissolve
out the oily matter, which will act as a repellant to the aqueous
chlorine solution. The chlorate of lime is dissolved in 10 parts of
water and filtered. The wings are transferred to a small quantity of
this solution and in an hour or two are thoroughly bleached, the veins,
however, retaining a light brown color. If the bleaching does not
commence readily in the chlorine solution the action may be hastened by
previously dipping them in dilute hydrochloric acid. When sufficiently
decolorized the wings should be washed in dilute hydrochloric acid to
remove the deposit of calcic carbonate, which forms by the union of the
calcic hydrate solution with the carbonic dioxide of the air. The wings
are then thoroughly washed in pure water and may be gummed to cards or
mounted on glass slides in Canada balsam, first washing them in alcohol
and chloroform to remove the moisture. If either of the solutions known
as _eau de labaraque_ and _eau de javelle_ are used in place of the
bleaching powder, no deposit is left on the wings and the washing with
acid is obviated. This process does not dissolve or remove the scales,
but merely renders them transparent, so that they do not interfere with
the study of the venation.
Prof. C. H. Fernald (_American Monthly Microscopical Journal_, I, p.
172, 1880), mounts the wings of Lepidoptera in glycerin, after having
first cleared them by the Dimmock process. After bleaching and washing,
the wings are dried by holding the slides over an alcohol flame, and a
drop of glycerin is then applied and a cover glass put on at once. By
holding the slide again over the flame until ebullition takes place the
glycerin will replace the air under the wings and no injury to the
structure of the wings will result, even if, in refractory cases, the
wing is boiled for some little time. The mount in this method must be
sealed with some microscopic cement, as asphalt or Brunswick black.
A method of mounting wings of small Lepidoptera for studying venation,
which I have found very convenient, is thus described by Mr. Howard in
_Insect Life_, Vol. I, p. 151:
"Some years ago we used the following method for studying the venation
of the wings of small Lepidoptera. We have told it since to many
friends, but believe it has not been published. It is in some respects
preferable to the so-called 'Dimmock process,' and particularly as a
time-saver. It is also in this respect preferable to denudation with a
brush. The wing is removed and mounted upon a slide in Canada balsam,
which should be preferably rather thick. The slide is then held over the
flame of an alcohol lamp until the balsam spreads well over the wing.
Just as it is about to enter the veins, however, the slide is placed
upon ice, or, if in the winter time, outside the window for a few
moments. This thickens the balsam immediately and prevents it from
entering the veins, which remain permanently filled with air and appear
black with transmitted light. With a little practice one soon becomes
expert enough to remove the slide and cool it at just the right time,
when the scales will have been rendered nearly transparent by the
balsam, while the veins remain filled with air. We have done this
satisfactorily not only with Tortricidae and Tineidae, but with Noctuids
of the size of _Aletia_ and _Leucania_. The mounts are permanent, and we
have some which have remained unchanged since 1880. Prof. Riley had for
some years before this been in the habit of mounting wings in balsam, in
which of course the scales cleared after a time."
Prof. John B. Smith recommends a modification of the Dimmock process of
bleaching the wings of Lepidoptera, publishing it in Insect Life, Vol.
I, pp. 291, 292, as follows:
"By the Dimmock process the wings are first acted upon by a saturated
solution of the chloride of lime, chlorine being, of course, the
bleaching agent. Afterward they are washed in water to which
hydrochloric acid has been added, to get rid of the slight deposit of
lime. The process is a slow one for thickly scaled, dark-colored
insects, and it occurred to me to try a mixture of the chloride and
acid, liberating the chlorine gas. The method was absolutely successful,
the wings decolorizing immediately and being ready for the slide within
two minutes. In fact, very delicate wings can scarcely be taken out
quick enough, and need very little acid. The advantage is the rapidity
of work and the certainty of retaining the wings entire, the chloride of
lime sometimes destroying the membrane in part before the bleaching is
complete. The disadvantage is the vile smell of the chlorine gas when
liberated by the combination of the two liquids. For quick work this
must be endured, and the beauty and completeness of the result are also
advantages to counterbalance the discomfort to the senses."
For further special directions for mounting, for microscopic purposes,
different insects and the different parts of insects, representing both
the external chitinous covering and the internal anatomy, the student is
referred to special works.