Between the collecting of the specimens and their final disposition in a
well-arranged cabinet, a good deal of mechanical work is necessary,
involving a skill and dexterity which can be thoroughly acquired only by
practice.
FIRST PRESERVATION OF LIVING SPECIMENS.--Larvae, pupae, or imagoes,
intended for rearing purposes, must be kept alive, and are best placed,
after capture, in tin boxes of various sizes, according to the number of
specimens to be put in each and according to the size or nature of the
food plant, etc., on or in which the specimens are found, and of which a
quantity must always be taken home. For larger tin boxes those known as
"Seidlitz powder boxes," described and figured below, which can be made
to order at any tinner's shop, are well adapted, and smaller tin boxes
of a convenient round form can be obtained of the watchmaker. The
collector will find it advisable to take with him on his longer jaunts a
larger tin collecting box as well as the smaller boxes, and for this
purpose nothing is better than a good botanist's collecting can or
vasculum. All tin boxes used for entomological purposes should be tight,
and the cover should so fit that it neither drops off too readily nor
closes too tightly. Larvae of Lepidoptera and Tenthredinidae should be
placed in a box with a quantity of the leaves of the plant on which they
were found. Larvae, especially of Coleoptera, found in the earth or in
decayed wood, should be placed in a box filled with such earth or wood,
so as to prevent shaking or rattling about. Larvae found in roots or
stems of living plants can generally be reared to maturity only if the
whole plant with a quantity of the surrounding soil is taken home, and
for this purpose the large collecting box, just mentioned, is very
useful. Most Coleopterous or other larvae found under bark or in solid
wood can be reared only if large sections of the wood are obtained and
the larvae are full grown or nearly so. This holds true, also, of species
breeding in seeds and with most leaf-mining species. The greatest
difficulty is experienced with carnivorous Coleopterous larvae, and care
should be taken with such not to inclose two or more specimens in one
box. Most larvae die quickly if placed in an empty box, and this is
especially true of predaceous species; so that it is always advisable to
pack the box with moist soil, decaying wood, leaves or other similar
substance. Aquatic larvae should be carried in tin boxes filled with wet
moss or some water plant, for, if placed in corked vials with water,
they die quickly.
KILLING SPECIMENS.--Specimens not intended for rearing should be killed
immediately after capture unless for each specimen a separate vial or
box can be provided. If a number of miscellaneous insects are put in the
same vial the stronger specimens will, in a short time, crush or
otherwise injure the more delicate ones or the predaceous species will
devour any others they can master. But even where the specimens are
killed immediately the following rule should be observed: Do not put
large and small specimens in the same vial, but provide a larger bottle
for the larger specimens, and one, or still better, several, smaller
vials for the medium-sized and very small specimens. The importance of
this rule is recognized by all experienced collectors.
There are several methods of killing insects, each having its own
peculiar advantages and drawbacks.
_Alcohol._--The use of alcohol will, on the whole, prove the most
satisfactory method of killing Coleoptera, many Hemiptera, some
Neuroptera, and larvae of all sorts. Only the best quality of alcohol
should be used, but it should be diluted with from 30 to 40 per cent of
pure water, the greatest care being taken to keep the alcohol as clean
as possible. During the collecting a mass of debris and dirt is apt to
be thrown into the bottle, and when this is the case the alcohol should
be changed even during short excursions. At any rate, upon the return
from the excursion, the specimens should be at once taken from the
bottle and washed in pure alcohol in a shallow vessel. The larvae and
other material intended for permanent preservation in alcohol should be
transferred to suitable vials and the material to be mounted cleansed
with chloroform or acetic ether and then prepared for the cabinet. If it
is inconvenient or impossible to mount the Coleoptera, etc., soon after
the return from the excursion they should be washed, dried, and placed
in pill boxes between layers of soft paper, or they may be replaced in a
vial with pure alcohol. On longer collecting trips, lasting several days
or weeks, specimens will keep thus very well, provided they are not
shaken up, and this can be prevented by filling the empty space in the
vial with cotton or soft paper. If the bottle is a large one and
contains many large specimens the alcohol should be renewed three or
four times at intervals of eight or ten days; otherwise the specimens
are liable to decompose. Small and delicate specimens, if they are to
be kept in alcohol, should be treated with still greater care. Upon the
return from the excursion they should also be cleaned in pure alcohol
and placed in small vials into which a very few drops of alcohol, just
sufficient to keep the contents moist, are poured. The vial should be
corked as tightly as possible and the specimens will keep pretty well
for an indefinite time.
The drawbacks to the use of alcohol are: 1st, that all hairy specimens
are liable to spoil; 2ndly, that all Coleoptera with soft integuments
spread the wing-cases apart if kept too long in it. The advantage of the
alcohol is that it is the simplest and least troublesome fluid for
naturalists traveling in distant countries who are not specialists in
entomology. Specimens killed in alcohol are also less liable to be
attacked by verdigris when pinned than those killed by some other
method. Rum, whisky, or similar strong alcoholic liquors may be used as
substitutes where no pure alcohol can be obtained, but are not
especially to be recommended.
_Chloroform and Ether._--Killing with the fumes of _chloroform_ or
_ether_ (sulphuric or acetic) or _benzine_, or some other etheric oil,
is often practiced and advocated by those who, for any reason, dislike
the use of alcohol or object, on account of its poisonous nature, to the
use of cyanide of potassium, and they are of especial value in the case
of butterflies and moths, Hymenoptera and Diptera. "A small and stout
bottle of chloroform or ether, with a brush securely inserted into the
cork (Fig. 89), will be found very serviceable. A slight moistening
through the air net will stupefy most insects caught in it, and
facilitate their removal to the cyanide bottle; while a touch or two
with the wet brush under the head and thorax, will kill the more
delicate specimens outright, without in the least injuring them. Another
way of using chloroform is by means of a small, hollow tube passed
through the cork, what is called jeweler's hollow wire answering the
purpose. The liquid evaporates more readily in such a bottle, and I
altogether prefer the first mentioned. Some large insects, and
especially female moths, whose size prevents the use of the ordinary
cyanide bottles, are difficult to kill. With these, fluttering may be
prevented by the use of chloroform, or they may be killed by puncturing
the thorax or piercing the body longitudinally, with a needle dipped in
liquid cyanide, or oxalic acid. A long bottle with a needle thrust into
the cork may be kept for this purpose; but the needle must be of ivory
or bone, as those of metal are corroded and eaten by the liquids. * * *
[Illustration: FIG. 89.--Chloroform bottle with brush.]
"For killing small and delicate moths which have been bred, I find
nothing more handy than chloroform. They may be caught in turned wooden
boxes which are kept by every druggist; and a touch of the chloroform on
the outside of the box immediately stupefies them. It has a tendency to
stiffen them, however, and they are best set immediately after death."
[Illustration: FIG. 90.--Bottle with liquid cyanide.]
[Illustration: FIG. 91.--The Cyanide bottle with paper strips to give
support to the insects.]
A piece of heavy blotting paper or heavy cloth soaked with chloroform or
ether or benzine and placed at the bottom of a jar or bottle makes an
excellent killing bottle for large-sized insects. For smaller specimens
the collecting vial should be half filled loosely with narrow strips of
soft paper, upon which a few drops of the liquid are poured, not so
much, however, as to wet the paper. While collecting, the vial must be
kept closed as much as possible. Some collectors prefer chloroform,
others ether. If this method of killing is practiced with the necessary
care, there is no objection whatever to it; the specimens are not wetted
as they are in alcohol, and remain cleaner than those killed by any
other method. The drawback is that the substances mentioned evaporate
very rapidly and have to be renewed even on short excursions. On account
of this great volatility, one can never be certain that all the
specimens in the collecting bottle are dead after a given time and there
is always some danger that one or the other of the hardier insects may
regain activity. What mischief such revived specimens are capable of
doing, many collectors have experienced to their sorrow. Another
disadvantage of these volatile substances is that if used in too large
quantities they will, in delicate specimens, especially beetles, cause
an extension of the soft ligaments between the head and prothorax or
between the latter and the mesothorax, and thus bring the specimen into
an unnatural position, or cause the head, or head and thorax to drop
off.
_Cyanide of Potassium._--The method of killing which, of late years, has
found most favor with collectors, is the use of cyanide of potassium.
For killing large sized specimens they are simply put in what is now
universally known as the "cyanide bottle." This may be constructed as
follows:
Take a 2-ounce quinine bottle, or still better a shorter bottle with a
wide mouth; break up a quantity of cyanide of potassium into pieces of
convenient size (about a cubic centimeter); put these pieces in the
bottle so that they form an even layer at the bottom; mix in a
convenient vessel a quantity of plaster of Paris with water just
sufficient to make the mixture semifluid and then pour it over the
cyanide so as to cover this last to a depth of about 5 millimeters. The
bottle is then left open for an hour or two until the plaster is
thoroughly dry. The walls of the bottle are then cleansed from particles
of the plaster which may have splashed on them, and the bottle is ready
for use. If not used too frequently, especially in warm weather, it will
last for an entire year or longer. Bottles or vials of different sizes
can be prepared in the same way, and a very small cyanide vial which can
be carried in the vest pocket will be found most convenient for use on
all occasions. Fig. 92 represents a medium-sized chemist's test tube,
converted into a very convenient cyanide bottle, in which, however, a
cotton wad has been used to keep the poison in place. When the collected
specimens have been removed from the bottle the latter should be
carefully wiped clean with a piece of cloth or paper. The surface of the
plaster soon becomes dirty and, on account of the hygroscopic property
of the cyanide, more or less moist, especially during warm weather. The
cyanide bottle is, therefore, not well adapted for the killing and
temporary preservation of small and delicate specimens. This difficulty
can be altogether obviated by placing a circular piece of blotting
paper, cut to neatly fit the interior of the bottle, on the surface of
the plaster. This can be renewed once a week or so, or oftener if it
becomes necessary. It will frequently be advisable, also, especially in
the collection of Diptera, Hymenoptera, and other delicate insects, to
put a strip of blotting paper partially round the inner side of the
bottle. This will absorb any moisture which may gather on the inside of
the bottle and which would otherwise wet and injure the specimens. The
accompanying figure (Fig. 93) illustrates a bottle arranged as described
above. A similar result is attained by some collectors by partially
filling the bottle with narrow strips of bibulous paper to support and
separate the insects as shown at Fig. 91.
[Illustration: FIG. 92.--Pocket cyanide bottle.]
For delicate specimens, also, the collecting bottle may consist of a
test-tube of about the size of Fig. 92. This is half filled with loose,
thin strips of soft white paper. A piece of cyanide about the size of a
pea is then wrapped carefully in paper and so placed in the middle of
the strips that it can not come in contact with the sides of the
glass. Some prefer to pin the paper containing the cyanide to the
lower surface of the cork. The latter should be rather short and
tapering toward its lower end. It is longitudinally perforated through
its center by a round hole just large enough to insert a goose-quill,
which is cut straight at the lower end and obliquely at its upper end.
By means of this goose-quill the specimens may be introduced into the
bottle without taking off the cork. This form of cyanide bottle lasts
for only one day's collecting, except in cold weather, and in very warm
weather it is advisable to take two prepared bottles along, so that the
first used can be stowed away as soon as the cyanide begins to moisten
the paper strips. Most insects are quickly killed in such a bottle, but
some Coleoptera must be left in for five or six hours, while others
resist death for a still longer time. This is especially true of the
Coleopterous families Curculionidae, Trogositidae, and Tenebrionidae.
Submersion in alcohol will prove a satisfactory method of killing these
or other beetles with similar vitality.
[Illustration: FIG. 93.--The cyanide bottle with blotting-paper lining
(original).]
_Other Agents._--Prof. E. W. Claypole has found the use of benzine or
gasoline very cheap and satisfactory for killing Lepidoptera, as the
largest are at once killed thereby without injury to their scales.
(_Can. Ent._, XIX, p. 136.) He squirts it onto the specimen within the
net or in the open air by means of a druggist's dropping tube. Hot water
kills rapidly and leaves the specimens in good flexible condition for
mounting. The heads of large insects may be held for a few moments in
the water, while smaller specimens should first be thrown into a corked
bottle and the bottle submitted to heat. Where the laurel grows its
bruised leaves may be used in place of cyanide; they kill less quickly.
The leaves of the Laurel-cherry (_Prunus laurocerasus_), a plant
commonly grown in England for screens and hedges, are also used for this
purpose.
Some collectors, with indifferent olfactory sense, moisten the cork of
their boxes with creosote. Its killing power lasts for several days. A
few whiffs from a cigar, when nothing else is at hand, will also kill
many of the more tender insects.
SPECIAL DIRECTIONS FOR DIFFERENT ORDERS.--A few brief directions for the
special treatment of different orders may be given. Certain Coleoptera,
notably those of the Curculionid genus Lixus, are covered with a
yellowish pruinosity resembling pollen, which is of an evanescent
nature, so that if the specimens are collected and killed by the
ordinary methods, the pruinosity is completely lost. To preserve the
natural beauty of such species it is necessary to put each specimen
alive in a small vial and to kill it at once by means of a lighted match
held under the vial for a few seconds. In pinning or otherwise mounting
the specimen it should not be handled between the fingers.
Many Hymenoptera and Lepidoptera, especially species with yellow
markings, if kept for any length of time in a cyanide bottle, will
become discolored, the yellow changing to reddish, and hence such
insects should not be left longer than necessary in the bottle. If care
is exercised in this respect, no danger of discoloration need ordinarily
be feared. The chloroform collecting bottle may be used with these
insects if discoloration is anticipated. All the more delicate insects,
including Hymenoptera, Diptera, the smaller Lepidoptera, and the
Neuroptera, require special care in killing. Large numbers should not be
thrown into a killing bottle together, and plenty of bibulous paper
should be kept in the bottle to prevent moisture from accumulating and
wetting and ruining the specimens. It is frequently advisable to pin
Diptera, especially the hairy forms (as the Bee-flies), in the net and
transfer them at once to a cigar box containing a sponge moistened with
chloroform. When the collecting shears are used, the insects are always
thus pinned at once, which is, in fact, the only method of securing
them. This is also necessary in the case of many Lepidoptera. Delicate
Neuroptera may be killed by the use of the cyanide bottle, or,
preferably, placed at once in a vial of alcohol, as these insects, in
many instances, cannot be kept securely if pinned or mounted. Large
Lepidoptera, as the Bombycids, may be killed by pouring benzine,
naphtha, or chloroform over the thorax and abdomen. These substances
evaporate rapidly and do not appreciably injure the vestiture of the
insects. Some collectors, in the case of butterflies, seize them
dexterously between the thumb and finger, and give a sharp pinch on the
sides of the thorax. This will prevent the fluttering of the insect when
transferred to the cyanide bottle, and, if carefully done, the scales
need not be rubbed off. It is objectionable, however, because the thorax
is distorted and subsequent anatomical study interfered with, and, in
the case of moths, should never be practiced, as the thorax affords
important characters used in classification. Orthoptera may be killed by
the use of the cyanide bottle but should be transferred at once to the
vials of alcohol. If placed in a cyanide bottle, especially in the case
of Locusts (_Acrididae_), they are apt to exude colored juices from the
mouth, so that the specimens become soiled. Hence the use of vials of
alcohol is preferable, and these insects should never be thrown into
vials containing delicate insects of other orders. Plant-lice, together
with the plant which they infest, should be placed at once in vials of
alcohol, and specimens of the Aphides, representing all the forms
present, should be mounted on slides for microscopic examination. The
fixed forms of Coccids, comprising the majority of the species, require
no special treatment, and the leaves, twigs, or bark on which they occur
may be pinned at once and placed in the collection. The free forms are
treated as in the case of plant-lice.