Freezing
and heating. As discussed in sections on jars and bags,
and CO2, freezing is a preferred method of killing insect specimens.
Most specimens will die over night but some cold resistant insects
may require a week or more to die. Kept frozen, specimens do not
dry out and can later be processed by pinning and mounting them,
eliminating the need for a “relaxing jar” or procedure.
Once the specimen is thawed, legs and wings can be moved to position
them before letting them dry for display. They will also retain
color patterns such as eye colors in horse and deer flies that
quickly fade when the specimen dries. Insects can also be killed
by heating them above about 135 degrees F, which happens when insect-containing
containers are placed on the dash board of a car in the sunlight.
However, heated specimens become overactive and will be more likely
to injure themselves in the process. It is also cruel!
Killing
jar. Usually in field work, insects are collected into
a killing jar. Killing jars may be in any size but seldom need
to be larger than a pint. Select a jar with a tight fitting lid.
Killing jars can be made simply by adding a few strips of paper
towels to a jar and then adding a few drops of ethyl acetate. Most
nail polish remover has ethyl acetate as its main ingredient and
can be used rather than specially ordering ethyl acetate (Note:
some species like grasshoppers may kick off their hind legs in
the process of dying in these poisonous fumes). The paper allows
insects in the jar to keep separated and also picks up excess moisture.
More permanent killing jars are made with a layer of vermiculite
topped with a layer of plaster of Paris (mixed with water) then
allowed to dry. The exterior of the bottom of the jar can be covered
with fiber tape or duct tape for additional support. Label the
jar clearly with a poison notice. Avoid putting moths in the same
killing jar with other insects. It is best to keep a separate jar
for this group because scales from the wings rub off easily and
will adhere to the other insects in the jar.
Papered
specimens. Butterflies can be immobilized or killed while
in the aerial net. Grab and squeeze the specimen by the thorax
between the thumb and forefinger with the wings folded over the
back. The butterfly will be stunned or killed, depending on force
of squeezing and time. Thereafter, specimens can be slipped into
a glassine envelope or paper “triangle” (see description
below). Specimens can be stored in this manner or mounted, either
directly or after “relaxing” the specimen. Dragonflies
and damsel flies can also be stored in this manner.
Alcohol. Although
alcohols, such as rubbing alcohol or 70% ethyl alcohol (7 parts absolute
alcohol in 3 parts distilled water) makes an ideal killing fluid
for many (soft-bodied) insect specimens, and is an excellent fluid
to store preserved specimens, many soft-bodied insects need to be
preserved in a different solution before storage in alcohol-filled
vials (see Boiling larvae and KAAD sections). Lower concentrations
of alcohol are less effective and some specimens will lose more color
or turn black over time when stored in diluted fluid. Alcohol evaporates
easily. When storing insects in vials of alcohol, containers must
be examined periodically and fluid replenished if needed. Tight seals
on caps can reduce evaporation rates.
Boiling larvae and KAAD. Many insects, especially
caterpillars, lose their color when preserved directly in alcohol.
To improve the appearance of these insects they may be killed in
boiling water for a few seconds or first killed in a solution called
KAAD (available from a source of entomological supplies). KAAD
consists of a solution of: 1 part kerosene, 7-10 parts 95% ethyl
alcohol, 2 parts glacial acetic acid and 1 part dioxane.
Freeze
drying. Larval stages of butterflies and moths can be
preserved dry (versus in alcohol after being preserved in boiling
water or KAAD) by freeze-drying them in a vaccum. Specimens retain
color and hair (setae) patterns better using this method. Special
equipment is required, however.
