How to Preserve Insects
How to Preserve Insects
The next step after collecting insects is to preserve them permanently for future display and study. Insect larvae and soft-bodied and extremely tiny specimens are preserved in liquids. Isopropyl alcohol (70 percent) or equivalent is best. All others are preserved on specially designed insect pins. Large insects are mounted directly on pins, while those too small to be placed on pins are mounted on card points (Figure 14).
The wings of butterflies, moths, and dragonflies are spread to make the specimens more attractive and to aid in identification. All other insects should be dried with legs and antennae adjusted in the most lifelike manner possible.
Insect pins are available from any dealer of entomological supplies. Do not use common pins, because they rust and soon ruin valuable specimens. Additionally, only insects mounted on proper pins are acceptable in competition. Insect pins come in several sizes, but sizes No. 2 and No. 3 are most useful to the general collector.
Any insect that is large enough to be supported on a pin without breaking or otherwise being distorted is pinned directly through the body. Insert the pin through the body from top to bottom. The proper place of insertion depends upon the type of insect (Figure 15). The following rules are for pinning different types of insects so that the pin is placed firmly through the heavier parts of the body without destroying important identifying characteristics.
- Bees, wasps, flies, etc. - Pin through the thorax between bases of fore wings and slightly to right of middle line (Figure 15A).
- True bugs - Pin through the scutellum, which is the triangular area between the bases of the wings (Figure 15B).
- Grasshoppers, crickets, etc. - Pin through the prothorax or "saddle" slightly to the right of the center line (Figures 15C and 15D).
- Beetles - Pin through the forepart of the right wing cover near the centerline (Figure 15E).
- Butterflies, moths, dragonflies, etc. - Pin through center of thorax between the bases of forewings (Figures 15F and 15G).
A piece of 1-inch thick Styrofoam is an excellent aid for pinning or mounting specimens. As each specimen is pinned, push the pin into the foam until the insect rests on the surface with approximately one-quarter to one-third of the pin projecting above the insect to facilitate handling of the specimen. Adjust the legs, antennae, and wings to a lifelike position with forceps and hold them in place with extra pins if needed. Allow the specimen to dry in the desired position for 7 to 8 days before moving. To prevent sagging, the abdomens of soft-bodied insects, such as crickets, mantids, or walking sticks, can be further supported with two temporary pins crossed at an angle such that the abdomen rests where the pins cross. Pieces of light cardboard supported on other pins can also serve this purpose. Once dry, the specimen will retain the proper position and the temporary supports can be removed.
Flat sheets of Styrofoam or other porous material also provide a handy place for the temporary holding of pinned specimens while they are labeled, identified, or arranged in display boxes.
The appearance of a collection is improved vastly if all the specimens are mounted properly and at a uniform height on the pins (Figure 16). This is easily done by using a "pinning block." Such a block is made of wood, plastic, or metal. Metal blocks must be purchased, but the others can be made at home. The wooden block is cut from a soft piece of wood 1 inch square and 4 inches long, or it is built by gluing together four pieces of 1/4-inch finishing lath creating steps of 1/4, 1/2 and 3/4 inches (Figure 17). Small holes, slightly larger than the insect pins, are drilled through each of the four steps. After an insect is placed on a pin, either the head or the point of the pin is inserted in the desired hole and the specimen adjusted to the proper height (Figure 18). The block also is useful in adjusting labels to a uniform height upon the pins, thus improving the overall appearance of the collection.
Figure 19 illustrates the card-point method used to mount very small insects. Cut all triangular points to a uniform size, 3/8 to 1/2 inch long and approximately 1/8 inch wide at the base. Index card paper is a durable and sturdy material to use. A specialized point punch (Figure 19A) can assist in creating a supply of points very quickly. If a punch is available, cut a large supply at one time (Figure 19B), and keep them in a box for future use. This saves time and assures that the card points are uniform. When a point punch is unavailable, a pair of fine pointed scissors will suffice. A series of card points may be cut from the pre-measured template found here.
Mounting insects on card points is not difficult if you follow the correct procedure. Note from Figure 19C that the pin is pushed through the widest part or base of the triangle and the specimen is glued to the point.
First, put the card point on the pin, and place a small amount of white glue or clear fingernail polish on the tip. Use as little adhesive as possible so that body parts will not become unnecessarily covered by glue. Next, lay the specimen to be pointed on its back on the edge of a block or thick book in such a manner that the pin can be turned upside down and the card point pressed lightly against the insect. IT IS VERY IMPORTANT TO ATTACH THE CARD POINT TO THE RIGHT SIDE OF THE SPECIMEN. With a little practice, the specimen can be placed so that it is in the correct position when glued to the point. Slight adjustments can be made once pointed and before the glue dries.
How to Pin a Ground Beetle
How to Pin a Damselfly
How to Pin a Silkworm Moth
How to Pin a Hornworm Moth
If specimens are allowed to dry out or become brittle, they may shatter when being pinned. Dry specimens can be made soft and pliable again by placing them in a relaxing chamber for 1 or 2 days. To make a relaxing chamber, place 1 to 2 inches of clean sand or sawdust in the bottom of a large, airtight jar. The jar must be large enough to allow small dishes to be placed inside, and must have a screw type or other lid to create airtight conditions inside the bottle. Saturate the sand with clean water and add a few drops of carbolic acid (sold at most drug stores) to prevent mold growth. Place the specimens in shallow, open containers on the bottom of the jar, and fit the lid tightly on the relaxing chamber. Amount of relaxing time needed varies with the size of the insect and how dry it is when first introduced. Retrieve and mount specimens as soon as they are pliable enough to pin easily, but remember that they can be ruined if left in a relaxing jar too long. Relaxing the wings of dry butterflies and moths is essential to allow them to be properly spread.
The relaxing chamber should be used for emergencies, not as a general practice. It is always best to pin specimens within a few hours after collection and avoid the need for relaxing chambers.
All butterflies and moths, and sometimes other insects, are mounted with their wings spread. A spreading board is therefore an important piece of equipment for the insect collector. One board is sufficient for a beginner, but eventually the serious collector will prefer more and different-sized spreading boards to accommodate either large or small insects. Adjustable spreading boards that meet both purposes are available from entomological supply houses. Wooden spreading boards (Figure 20) also can be made at home, using the following materials.
- Two end blocks, 5 1/2 inches long and 1 inch square.
- Two soft wood top pieces, 16 inches long, 2 1/2 inches wide and approximately 1/2 inch thick. These pieces should be planed down to 3/8 inch thick on one edge.
- One flat strip of corrugated box paper, fiberboard or cork, 14 inches long, 1 inch wide and approximately 1/2 inch thick.
Nail the two top pieces to the end blocks, leaving approximately 1/2 inch between the thin edges. The cork or corrugated paper then is tacked beneath the top pieces to cover the opening and provide soft material into which insect pins can be inserted.
The top pieces can be sloped by cutting the top sides of the end blocks into shallow "Vs". This permits insect wings to dry in a slightly elevated position and allows for any sag that may occur after the specimen is removed from the board. Spreading boards with level top pieces are acceptable, but insects must remain on such boards longer for complete drying.
A less expensive spreading board is made from Styrofoam. The dense blue insulation-type Styrofoam used in house construction works best. Carve a groove to accommodate the body of the insect into a single block of this material or glue pieces of Styrofoam together to make a board similar in size and shape to the wooden one previously described.
Before attempting to spread an insect's wings, make sure the insect is fresh or thoroughly relaxed. Pin the specimen in the usual manner and at the usual height on the pin. Insert the pin into the middle slot of the spreading board and push down until the body lies in such a way that the wings are flush with the top pieces of board. Cut several thin strips of paper about 1/4 inch wide and 8 to 10 inches long. This paper helps secure the wings without rubbing the scales off or unnecessarily tearing the wings. Slip a paper strip between the wings (if they are upright) and use them to force the wings on one side down into position (Figure 21). Being careful not to tear the wing, pin the ends of the paper down to the board (B). Then, with a fine point or needle inserted behind the heavy front margin of each wing, pull to adjust the front wings until their hind margins form a straight line (right angles to the long axis of the body), and secure by placing additional pins in the paper strips (C). Work the hind wings forward in a similar manner until their leading margins are concealed beneath the front wings (D). Repeat steps for opposite wing (E).
After wings are secured, set the board aside for 10 to 14 days to allow the specimen to dry adequately.
Note: Incorrectly spread wings is the biggest error in beginning entomology collections. Proper spreading takes practice. Poorly spread specimens should be replaced before entering collections in competition.
Proper labeling of specimens should be first and foremost in the minds of those creating insect collections. Professional entomologists usually welcome the opportunity to study the insects of a well-preserved and labeled collection, because such collections supply distribution and timing records, as well as other information of value to the profession. There is pride and satisfaction in a collection that includes important scientific value.
To be of scientific value, each specimen must be accompanied by information including the location (county and state) and date (day, month, year) of its capture and the name or initials of the collector. To avoid confusion, the month should be written in roman numerals and should always occur between the day and the year. These data are printed on a small label (Figure 22) placed on the pin beneath the specimen. A specimen in a collection for scientific purposes frequently has secondary labels on the pin indicating the host or habitat of the specimen or its identification (not required in beginning or 4-H club collections).
The maximum allowable size of pin labels in 4-H collections is not more than 7/8 inch long and 5/16 inch wide. Most professional entomologists use even smaller labels. Pre-sized labels are provided here and may be created by cutting directly from the page. Homemade labels are cut from stiff white paper, such as index card stock. Collectors find many advantages in cutting a large supply at one time for future use.
The most important label should be mounted closest to the insect. This label must have the name of the state and county where the insect was collected, as well as the date and the name of the collector. The label should be positioned in line with the length of the insect. Additional labels, indicating hosts and identification, may be placed lower on the pin and oriented as in Figure 23.
Cut all labels to the same size and from the same card stock to vastly improve the appearance of your collection. Carefully and neatly print information on the label to improve the appearance and the utility of the collection. Fine-point black pens are the best choices for attractive and legible labels. When you plan a large collecting effort in a single habitat or on a single day, use a computer to print partial labels in small type so that only the date and initials of the collector are filled in by hand to save time and effort.
Use a pinning block to place labels at a uniform height on the pins and always orient the labels so that all are read from the same side. These tips make for a very eye-catching display.
Preserve larval stages of insects and other soft-bodied specimens immediately by dropping them directly into a 70 to 90 percent ethyl or isopropyl alcohol solution. When collecting in the field, carry a few small vials of preservative fluid to store specimens.
An even better method of preserving caterpillars, grubs, and maggots, is to carry them home alive in separate plastic or glass containers, then submerge them for 1 to 2 minutes in boiling water. After this they can be immediately placed in the vials of alcohol. This process kills bacteria in the digestive tract and prevents discoloration. After a day or two, the liquid may become discolored. When this happens, transfer the specimens permanently to fresh alcohol solution.
Specimens in vials must be labeled exactly as described for pinned specimens with two exceptions. Labels must be written with a soft-lead pencil or with India ink so that the writing does not disolve or run. Only one label should be used, thus append any information such as host and identification to the bottom of the label. Cut labels longer to allow for this. Labels must be included with the specimen inside the vial. Do not attach them to the outside as this has proven to be an unreliable method of labeling.