6.1 - Housing the Collection

The adoption of standard equipment for housing a collection is advantageous as it assures uniformity of containers when additions are necessary. Standard equipment is obtainable from any of several supply houses.

Material preserved in liquid usually needs no attention other than occasional replacement of preservative and stoppers. Small vials may be stored in racks so that the stoppers are not in contact with the liquid. The use of storage racks for vials expedites rearrangement and examination of the material. Vials should be examined periodically to be sure the specimens do not become dry. If it is not possible to inspect the vials frequently, those containing larvae or large insects should have their stoppers replaced by cotton plugs. Several such vials can be placed upside down in a single large jar filled with preservative. Use of cotton plugs is not recommended for very small or delicate specimens because they may become entangled in the cotton fibers. Jars with screw tops or clamping lids, as are used in home canning, are ideal, but jars specifically designed for museum use can be obtained from biological supply houses. Stoppers of neoprene or other synthetic materials generally are superior to cork stoppers, but good quality cork stoppers are usually preferred to plastic screw tops, which often are easily broken. Many of the newer flanged plastic stoppers are excellent.

Microscope slides are usually stored in wooden or plastic boxes obtainable from biological supply houses. The inner sides of the boxes are slotted to hold the slides vertically and to separate them from one another. Slide boxes are available in sizes made to hold from 50 to 100 or more slides. If the slides are to be stored vertically, it is important that they be thoroughly cured before storage or the cover glasses may slip. Some workers store the slide boxes on their sides so that the slides rest horizontally. This is especially desirable if the slides are made with Hoyer's medium, which may become soft under very humid conditions. Several slide-filing systems are available from suppliers, but whatever system is used, care should be taken to assure that additional similar equipment will be available in the future for expansion of the collection.

For large slide collections, there are slide boxes or cabinets which contain numberous "drawers" in which slides like in a horizontal configuration.

 

Figure 33. A U.S. National Museum drawer with foam-bottomed unit trays

Small plastic slide boxes, usually made to hold five slides, are convenient for keeping slides in a unit-tray system although it is usually best that pinnned specimens and slides not share the same unit. This is especially desirable when genitalia are mounted on slides, because it is readily apparent to visiting researchers examining the pinned specimens that such slides are available.

Pinned specimens are best kept in one of the types of standard, commercially available insect drawers, available in U.S. National Museum (fig. 33), California Academy of Sciences, Cornell, or Schmitt sizes. Larger collections usually use the unit-tray system, with various sizes of unit trays made to fit into a drawer. The pinning bottoms of both the unit trays and boxes are now generally made of polyethylene foam. The older standard was pressed cork, but that was extremely variable in quality and usually contained enough tannin to corrode pins and eventually to cement the pins firmly into the pinning material. Polyethylene foam is now available in large sheets to be cut to the desired size and cemented into boxes or unit trays.

A serviceable substitute for polyethylene is 6-mm-thick balsa wood boards, obtainable from modelmaker supply houses. These boards should be individually selected for softness because they are frequently excessively hard. Another good substitute, especially for temporary storage of pinned specimens, is double-thickness corrugated board, which is often used to separate layers or rows of cans in cartons. Single-thickness corrugated board will not hold an insect pin firmly, and the harder board used for making cartons is not usable.

Any box used to store insect specimens must be nearly airtight to keep out museum pests-dermestid beetles, psocids (booklice), and certain other insects-which will quickly devour or at least make a shambles of a collection. These pests find their way even into the best boxes or insect drawers, and constant vigilance is necessary.

6.2 - Protecting Specimens From Pests and Mold

Freezing of storage containers is the safest method of fighting or preventing infestations of insect pests such as dermestid beetles inside containers. Containers should be put in a heavy polyethylene bag and placed in the freezer for a period or about 2-5 days at a temperature of -200C to -250C (-4 to -13F) degrees or colder. The length of time necessary is dependent on the container and any insulation surrounding the specimens. Specimens should be dry so that there is no danger of crystallization. Incoming packages should be frozen as received so that any pests hiding in shipping materials are killed.

Fumigation of all insect storage boxes may be necessary from time to time. The best made insect drawers provide space for chemical fumigants. Two of the most widely used fumigants are paradichlorobenzene (PDB) and naphthalene, both of which are obtainable in balls or flakes. Never mix PDB with naphthalene as they react chemically and produce a liquid that may damage the collection. It should be noted, that most major collections are now moving away from the use of solid fumigants because of health concerns and in some jurisdictions, it is now against regulations to use some fumigants.

Solid fumigants should be used with caution when placed in a box of pinned specimens, and under no circumstances should loose material be included. If crystals or flakes must be used, a small quantity should be placed in a little cloth bag or in a pillbox with the top perforated with tiny holes. This container should be pinned firmly into one corner of the box of specimens. Mothballs may be pinned in a box by attaching the mothball to the head of an ordinary pin. This is done by heating the pin and forcing its head into the mothball. When moving boxes, be careful that the mothballs and fumigant containers do not come loose and damage the specimens.

To kill pests that are actively damaging a collection, you may need to use a liquid fumigant, which acts more rapidly than solid fumigants. Examples of liquid fumigants are carbon disulfide, carbon tetrachloride, chloroform, ethyl acetate, and ethylene dichloride. Because liquid fumigants volatilize rapidly, may be flammable, and are toxic to humans, use extreme care. Work outdoors if possible and use some kind of fumigation chamber. A large plastic bag will serve this purpose. A cotton ball, saturated with a liquid fumigant, may be placed in the infested box, which in turn is placed in the fumigation chamber or plastic bag. One day in the chamber usually is sufficient to kill the pests.

To keep museum pests out of Riker mounts and other display cases, sprinkle naphthalene flakes on the cotton when the mount is prepared. Papered specimens should be kept in boxes with PDB or naphthalene.

All fumigants are toxic to humans to some extent, and most of them are highly flammable. Even PDB, commonly sold for household use, is now considered toxic to some degree. Before using any fumigant, it is well to find out as much as possible about its properties.

In general a combination of mechanical control, sanitation, and the use of inert compounds will help prevent populations of pests from increasing. It is important to keep dust and dirt to a minimum by vacuuming and sweeping. Keep plants to a minimum since these can house and supply food to a variety of potential pests. Make sure that all windows are screened and elminate cracks and crevices around doors and heating ducts where possible. Keep food under cover.

To provide additional control around cabinets, etc. several compounds such as diatomaceous earth, boric acid, and juvenile hormone analogs can be used to control pests such as cockroaches and other resident insects.

Another serious problem, especially in moist, warm climates, is mold, a kind of fungus that readily attacks and grows on insect specimens. Once a specimen has become moldy, nothing can be done to restore it. If only a few filaments or hyphae of mold are present on a specimen, they may be removed carefully with forceps or with a fine brush. The specimen then should be dried in a warm oven. Only keeping the collection in a dry place will prevent mold. In humid climates it is sometimes necessary to keep insect and other kinds of collections in rooms with artificial dehumidification. Some microscope-slide mounting media are also subject to molding.

Reference: Dawson 1992; Furth 1995; Kosztarab 1966; Strang 1992.