Herbert H. Ross

For making even a fairly large insect collection, only a small amount of equipment is required. A net and killing bottle are essential, and good work may be done with these alone. A greater variety of insects may be collected and with better results if a few more items are added to the list. Here is an outfit that will be found very satisfactory in the field.

1. A strong beating net for general sweeping and an additional light net to be used for moths and butterflies.

2. Killing bottles, several small and one or two large ones.

3. A pair of flexible forceps, 10 to 12 centimeters (about 4 to 5 inches) long, with slender prongs.

4. One or two camel’s-hair brushes for picking up minute insects.

5. A few vials or small bottles containing fluid preservative.

6. Folded papers for butterflies.

7. A few small tins or boxes lined with cellucotton.

These items may be purchased from commercial supply houses such as those listed on page 71. Many items, however, may be made by the collector at nominal cost.

Nets

Nets are the most important items in the collecting kit of the entomologist. For this reason nets should be rigidly constructed and handled with care.

Construction.—Nets may easily be made at home. The necessary parts are a handle, a loop or ring to be attached to it, and a cloth bag to be hung from the loop, figs. 1 and 2. The handle should be strong and fairly light. At the net end, fig. 1a, a groove is cut down each side to receive the arms of the loop. The grooves are as deep as the thickness of the wire used in the loop; one groove is 3 inches long and the other 2½ inches; and each ends in a hole through the handle at right angles to the length.

The loop, fig. 1b, is made of steel wire, preferably three-eighths-inch piano wire, which if bent by rough usage springs back into shape and will stand a great deal of hard wear. The wire is shaped, as the figure shows, to form a loop with two straight arms, the tips of which are bent at right angles toward each other. The arms and hooks thus formed must be exactly long enough to fit along the grooves and into the holes in the handle. After the bag or net has been attached to the loop, and the wire has been fitted to the handle, the joint may either be wrapped tightly with wire, fig. 1c, or bound by a metal cylinder or ferrule slipped over the arms of the loop, fig. 1d.

The bag, about twice as long as the diameter of the loop, should be tapered at the bottom. It is made from four pieces of cloth, each cut in the shape of fig. 2a, and a narrow strip or band of stout muslin or light canvas, 2b, which is to bind the bag to the wire loop. The four pieces are sewed together to form a cone-shaped bag, and one edge of the band is sewed to the top edge of the bag.

The bag may be attached to the wire loop in either of two ways. The band may be folded over the loop and sewed so that the attachment is permanent; or it may be folded over, sewed, and then slipped on the loop before the latter is fastened to the handle. In the latter case the bag must be open along one seam just below the handle a sufficient distance to allow the band to slip on and around the loop; this vent may be closed with a string lacing after the net is on the loop, and the whole fastened to the handle. A combination of this arrangement with a ferrule binding the loop to the handle is most convenient, for it allows the bag to be removed at will and a lighter or heavier one substituted according to the needs of the collector.

Fig. 1.—Net loop and handle. The short grooves cut opposite each other at the small end of the handle, a, end in holes through the handle that receive the hooks of the loop arms, b. The loop may be permanently bound to the handle with wire, c, or a removable joint may be effected with a metal ferrule that can be slipped up and down, d.

Fig. 2.—Bag and completed net. The bag is cut from four pieces shaped as in a, and the top edge of the bag is bound with a narrow strip of stout muslin or light canvas, b, by means of which the bag is attached to the loop. After the bag is on the loop, the back vent may be closed with a string lacing, as shown in the figure. This closing, which keeps the back of the net from gaping, prevents the escape of the most active insects through the back opening. The handle pictured here is a removable type, fig. 1d.

General Purpose Net.—Loop, heavy wire, 12 inches in diameter; bag, strong unbleached muslin or light duck, 20 to 24 inches long; handle, hardwood stick, 24 to 30 inches long.

Butterfly Net.—As above but with a longer handle and a bag of good quality marquisette or fine nylon netting.

Combination Net.—A net that includes the features and uses of the two nets described above and is a better collecting instrument may be conveniently made instead, although at slightly higher cost because of the better materials. Its loop, of 7½ gauge (three-eighths inch) piano wire, is 15 inches in diameter and allows a greater area to be covered with each sweep. The bag, of finest bolter’s silk or best quality marquisette, is 24 inches long and serves equally well for the capture of delicate insects and for beating. The handle, of straight-grained hickory or ash, is 40 inches long and permits the collector to cover greater areas in sweeping. If a cheaper net is desired, one of unbleached muslin will be satisfactory for general use.

Care and Use.—All nets are easily ripped and for this reason should be kept away from barbed wire and from thorny trees, such as locust and red haw. Also, they should be kept dry. Moisture rots the fabric, making it more easily torn. Most insects caught in a net while it is wet are unfit for a collection.

Flowers, herbs, and boughs should be swept with a sidewise motion. A sidewise sweep will collect more insects than an upward or downward sweep and at the same time mutilate less. If care is taken not to damage flowers or foliage, the same patch of plants may be visited several times with profit. The contents of the bag should be removed after every few sweeps or strokes. This practice will prevent damage to the insects caused by being jostled about in the net with a large amount of debris.

Killing Bottles

The best killing agents for use in bottles are either potassium cyanide or calcium cyanide. These compounds give a concentration of deadly fumes sufficient to kill most insects in a very short time, which is desirable. Generally, two sizes of bottles are used, and in either of them one of these cyanides may give good results. Only a small supply should be purchased at a time, as they deteriorate rapidly.

Construction.—A pyrex glass test tube or strong ring-necked vial, about three-quarters inch wide and 4 to 6 inches long, makes a good cyanide bottle of the smaller size, fig. 3. Put about three-quarters inch of granular potassium cyanide or calcium cyanide flakes in the tube or vial. Cover with a tight plug of cellucotton, on top of which put one or two loose plugs. Instead of cellucotton, you may use sawdust and a plaster of Paris batter. In the latter case, cover the cyanide with one-quarter inch of sawdust and over it pour one-quarter inch of newly mixed, thick batter of plaster of Paris and water. Allow the batter to harden for a few hours; then keep the bottle tightly corked except when it is being used.

Fig. 3.—Cyanide killing bottles. The lethal chemical, 1, is potassium cyanide or calcium cyanide and is covered with a layer of cellucotton, 2, or sawdust, 3, and plaster of Paris, 4. The rest of the bottle is filled with soft, loosely crumpled, lint-free paper, which should be changed whenever it gets damp. The bottles should be tightly corked and labeled POISON. The collector should not test their strength by smelling.

The larger cyanide bottle, fig. 3, which should be sturdy, may range in capacity from one-half pint to a quart. In the larger bottle, the cyanide should always have the plaster of Paris covering. The layer of sawdust and plaster should be a little thicker than that for the smaller bottle.

Care and Use.—Label all killing bottles and other containers of cyanide conspicuously with the word POISON; keep them tightly corked and away from children or adults who do not realize the extreme deadliness of the compounds. Never test the strength of a killing bottle by taking the cork out and smelling the contents. As an added precaution and safeguard to the collector, tape the bottom of the cyanide bottle to protect it against breakage.

The bottle should be almost entirely filled with loosely crumpled, soft paper, which should be changed whenever it gets damp. This paper will help keep the specimens from rubbing against each other inside the bottle and thereby being damaged.

Each collector should have several cyanide bottles and follow carefully these practices.

1. Transfer insects from net to bottle by holding the uncorked bottle in a fold or corner of the net and crowding one or more of the specimens into it, or “running” the open bottle up the side of the net beneath the specimen or specimens. Most insects can be maneuvered into the bottle easily and the opening temporarily closed by the thumb, or the stopper can be put on. In obstinate cases, it may be desirable to stopper the bottle through the cloth of the net until the specimen is stupefied, after which the insect will drop to the bottom of the bottle.

2. Keep small, delicate insects in a bottle by themselves. Such insects as large beetles are apt to mutilate small flies and other delicate insects in the same bottle.

3. Keep a special bottle for moths and butterflies. When these die they shed large quantities of scales, which stick to and partially spoil other insects.

4. Keep the inside of the bottle dry. Cyanide bottles “sweat”; that is, moisture both from the insects and the plaster condenses on the inside of the bottle. Moisture will mat the hair and appendages of insects and discolor the bodies. Do not crowd the bottle with large insects, especially juicy ones like grasshoppers. Change the paper frequently. Wipe out the bottle with paper or cloth, which should be carefully disposed of in such a way that it cannot poison persons or pets. Keep the killing chemical out of cuts and mouth. Wash hands with care after handling the chemical.

5. Take insects out of the bottles soon after they are dead. Cyanide fumes quickly turn many yellows to red or orange, and also make small specimens brittle so that legs and other parts break off easily.

6. Empty the insects out of the bottles before they have accumulated in a ball at the bottom. To do so will prevent damage to the smaller specimens and discoloration due to “sweating.”

7. Dispose of a cyanide bottle when it will no longer kill insects quickly. Substitute a fresh bottle and you will save time in the field. Be sure to dispose of old bottles in such a way that their deadly contents are out of reach of children and pets.

Aspirators or Suckers

Small, rapidly moving insects, such as leafhoppers, diminutive beetles, and flies, may be collected by using an aspirator or sucker, figs. 4 and 5.

Construction.—An aspirator can be made from a capsule vial (available from a drugstore) or from a piece of glass tubing. A small olive bottle may be substituted for the vial.

The following items are needed for the vial aspirator, fig. 4: a vial, 1¼ inches in diameter and 3 or more inches long, a two-hole rubber stopper with openings to fit one-fourth-inch diameter glass tubing, 16 inches of one-fourth-inch diameter glass tubing, rubber tubing 24 inches long to fit over the glass tubing, a small metal file (the triangular type is best), a small piece of cheesecloth, some string, and a bunsen burner. Construct the vial aspirator according to the following directions and as shown in fig. 4.

1. Cut the glass tubing into three pieces, 3 inches, 8 inches, and 5 inches in length. To cut the tubing, score it with an edge of the metal file; then hold the tubing with both hands so that the thumb of each hand is on the side of the tubing opposite to the scored mark; break the tubing away from the body by exerting pressure with the thumbs.

2. Make a slight bend in the center of the 8-inch piece of tubing and a right angle bend in the 5-inch piece, as follows: hold one piece of glass tubing with both hands and place the center of it in the blue flame of the bunsen burner; rotate the tubing slowly. When the glass glows yellow, it begins to soften. Bend the tubing to the desired angle. Then quickly withdraw the tubing from the flame.

3. Heat one end of the 8-inch piece of glass tubing in the bunsen burner, slowly rotating the tubing so that the sharp edges melt slightly and round out; then allow the tubing to cool. Heat one end of the 3-inch tubing in the same manner. Smooth the remaining rough edges of the glass tubing by heating them slightly.

Fig. 4.—Vial type of aspirator or sucker. End g is placed in the mouth; c is used to pick up the insects. Shown also is a cyanide cork, h-i, which is used to kill insects in the aspirator.

Fig. 5.—Tubing type of aspirator. Parts for this aspirator should be compared with equivalent parts for the aspirator shown in fig. 4. Noted especially should be the position of the glass tube, c, and the length of the rubber tube, f.

4. Insert the 8-inch and 5-inch pieces of glass tubing into the rubber stopper. The longer piece, fig. 4c, should project about 1½ inches into the vial. The shorter piece, fig. 4d, should project about three-fourths inch.

5. Over one end of the 5-inch piece of glass tubing, fig. 4e, tie two thicknesses of cheesecloth securely with string.

6. Over the other end of the 5-inch piece, slip one end of the rubber tubing, fig. 4f.

7. Into the other end of the rubber tubing slip the 3-inch piece of glass tubing, fig. 4g, so that the rounded end of glass is exposed.

8. Complete the assembly of the aspirator by placing the rubber stopper snugly into the vial. The vial aspirator is now ready for use.

If a piece of glass tubing 1¼ inches in diameter and 8 inches long is available, then a tube aspirator can be made, fig. 5. In making a tube aspirator, use two one-hole rubber stoppers, 5b. Cut the pieces of glass tubing as shown in fig. 5c, 5e, and 5g. Using a piece of rubber tubing, 5f, complete the minor details as described for the vial aspirator, not forgetting the cheesecloth, 5e, and assemble the parts as shown in fig. 5.

Use and Care.—To catch an insect with the aspirator shown in fig. 4 or fig. 5, put end piece, g, in your mouth, grasp the vial or tube, a, in your dexterous hand, aim the intake tube, c, at the insect and almost touching it; suck suddenly and hard. The air current pulls the insect in; the insect usually does not find its way into the intake tube to crawl out. The cheesecloth, e, prevents the insect from being sucked into your mouth.

To kill insects in the aspirator, use a small cyanide bottle, 4i, which is inserted in a cork, 4h, that has been partially bored through to receive it. This cork should be the exact size of the vial or tube for which it is intended.

Fig. 6.—Sifter with hand grips. Debris containing insects is sifted over a piece of white oilcloth. The sifter, not more than half full, is shaken gently at first and then violently. Finally the debris that cannot be shaken through the sifter is emptied on the oilcloth, and specimens too large to go through the mesh of the sifter are captured. Patience is required to get the best results with the sifter, which provides one of the best methods for winter collecting.

To use the cyanide cork with the vial aspirator shown in fig. 4, simply exchange the corks. If the glass tube aspirator is used, plug the intake tube, 5c, with a tapered paper plug or a leaf, jar the insects away from the stopper at the opposite end, remove this stopper cautiously, and quickly insert in its place the cyanide cork. When the specimens are stupefied, they may be transferred to another bottle.

The cyanide corks are highly poisonous. Between times of use with an aspirator, keep each of these corks inserted tightly in a bottle or vial labeled “POISON,” as in fig. 3.

Sifter

Perhaps no special collecting method results in more interesting, rare, and diverse kinds of insects than that involved in sifting rotten logs, leaf mold, and other forest and prairie ground cover. To do this type of collecting, provide yourself with the following:

1. A stout sifting sieve about 12 by 12 inches and 4 to 6 inches deep, fig. 6. The bottom may be wire screen of any desired mesh; usually 8, 10, or 12 meshes to the inch give good results.

2. A sturdy piece of white oilcloth about 18 inches or 2 feet square.

3. Collecting equipment, including an aspirator, camel’s-hair brush, forceps, vials, and killing bottle.

Material such as leaf mold is placed in the sieve and this is shaken over the white oilcloth, which has been spread on a level spot on the ground. The small insects fall on the cloth and can be picked up with the aspirator or the camel’s-hair brush. Many insects feign death when they fall to the oilcloth and they are difficult to detect in the bits of sifted material until they “revive” and start to move.

In late fall and winter, sifting provides one of the most profitable types of collecting; in any season, it will turn up such things as rare spiders and beetles. Sifting is most successful for finding large, active insects. For small, slow-moving forms, Berlese funnels offer a better collecting method.

Berlese Funnel

When you are wandering through woods or fields, do you realize that you are stepping on more insects than you ever see? The ground cover and soil are inhabited by a vast assemblage of little animals that are seldom seen by the casual collector. Because many of these animals are exceedingly minute, they are difficult to see and collect by ordinary methods.

Construction.—The most efficient method for collecting this fauna is by the use of Berlese funnels, named after the Italian entomologist Berlese (pronounced Bur-lazy), who first used them extensively. A Berlese funnel is a very simple apparatus, consisting of a fairly long funnel, suspended wide end up, with, a screen placed about a third of the way down the funnel; heat is applied either around the upper portion or over the top of the funnel, and a container of preservative, preferably 80 per cent ethyl alcohol, is placed at the small bottom opening. Leaf mold or other material is placed on the screen, the heat source is turned on, and soon the animals begin to leave the drying sample and migrate downward, dropping into the preservative.

Fig. 7 illustrates a funnel that has proved very satisfactory; it is 15 inches from top to bottom, and the top has a diameter of 12 inches. The bottom opening, seven-eighths inch in diameter, fits into the mouth of the bottle containing the preservative. Three angled brackets or hangers are soldered inside the funnel to provide a rest for the screen, which is made of quarter-inch or eighth-inch mesh hardware cloth; the mesh used depends upon the type of sample. A battery of several funnels in a rack, fig. 8, will allow the collector to sample several kinds of material at the same time.

If steam is used as a source of heat, the small copper lines that conduct it act as a partial support for the funnel by encircling it about halfway between the screen and the top; a piece of cloth is tied tightly over the top of the funnel to prevent the upward escape of animals. If an electric light is used for heating, it should be hung directly over the center of the funnel, no cloth should be tied over the top, and the light should have a reflector nearly as wide as the top of the funnel.

Care must be taken not to heat the sample too rapidly. Otherwise, either moisture will condense in the lower part of the funnel and trap many of the animals working their way toward the bottom, or the heat will kill many of the organisms before they have an opportunity to move out of the sample. An application of heat sufficient to dry the sample in 4 or 5 days is usually satisfactory.

The Berlese funnel is extremely useful for collecting many groups of beetles (particularly Staphylinidae), thrips, springtails, many groups of parasitic Hymenoptera, ants, mites, pseudoscorpions, millipedes, centipedes, and a wide range of other minute animals that live in soil, surface cover, logs, or bark.

Collecting Berlese Samples.—Many different habitats and micro-habitats provide good samples for the Berlese funnel. You will find that, for general collecting, various types of ground cover are excellent; for leaf mold samples, scrape off and discard the dry surface leaves and scoop up the lower, rotted layers of leaves together with an inch or two of the adjacent soil. You may encounter especially good samples where leaves have blown in along the edge of a log. In such a situation, take some of the log bark with the sample. Collect rotten log samples in large hunks and break them up just before putting them in the funnel. From either standing stumps or fallen logs in which the wood is still too hard to break up, collect the loose bark, as it is often quite productive. Frequently, if you roll a log over, you may find animal runs under it; the debris and earth under and around these runs, together with animal nests, frequently give unusual catches, such as larvae and adults of fleas and rare ticks. Especially productive are samples taken from the interior of a standing hollow tree; from the bottom of the hollow you can scoop out a foot or more of fine, rotten, woody material rich in rare insects.

Certain items placed in the funnel may produce distinctive and unusual catches. Recently deserted birds’ nests will give mites and, frequently, rare beetles, flies, and their larvae; mature or overmature mushrooms and bracket fungi are often rich in beetles, thrips, and maggots; bark of living trees may produce unusual thrips, springtails, and psocids; debris from aquatic habitats and from the wet edges of ponds and tiny streams may be productive of rare aquatic and semiaquatic forms. Moss is a good source of peculiar species of springtails, thrips, and beetles; the moss should be rolled up carefully while being transported.

Handling Berlese Collections.—In the field, put samples of leaf mold or other material in tightly woven cloth bags or strong paper bags for transportation. It is convenient to have small paper bags for mushrooms, nests, and other small items, and larger bags for ground cover, moss, and the like. When collecting ground cover and similar material, put in each bag enough of a sample so that it will not shake around loosely, but do not pack it tightly. Be sure that samples do not overheat while being transported.