How to Collect Insects
How to Collect Insects
Large insect collections may be made with a few pieces of inexpensive equipment. A net, insect pins, identification guide, collecting jars and display cases are the most essential and allow any beginning entomologist a great start. A few other pieces of equipment come in handy and enable the more advanced collector to obtain an even larger variety of specimens.
You can buy most equipment for catching, handling, identifying, and displaying insects from biological supply outlets. Some of these can be made at home. Both serve the purpose equally well. This booklet describes how to make or where to purchase the basic equipment for collecting and displaying insects. It also serves as a basic insect guide for identification and classification. As students gain experience, however, their identification skills will improve if they buy and use any of several field guides to insects. Many different field guides are available from bookstores and libraries. In most cases, the more color photos, the more helpful the guide.
All insect collectors use nets to help catch elusive insects. You can use a net in one of three ways.
- One is to sweep foliage. To sweep means to swing the net back and forth such that it scrapes the tops of plants and dislodges the insects that are feeding or resting there, causing them to fall into the open net. After a series of sweeps, the collector then carefully examines the insects caught in the net and selects the specimens of interest.
- Another, more common, way in which a net is used is by swinging it quickly through the air to catch flying insects such as bees, wasps, butterflies, dragonflies, and other wary insects.
- The third way is to use a sturdier net to collect insects from water.
Sweep nets, aerial nets, and aquatic nets can be either purchased from entomological supply houses or made at home. A general purpose net is one that is sturdy enough to sweep plants, yet light and porous enough to be swung quickly through the air. Variations in the basic plan or the materials used are common and can be adjusted to suit specific collectors needs.
Generally, a net (Figure 1) consists of a handle fitted on a heavy wire loop to which a bag is fastened. The bag is cone-shaped and twice as long as the diameter of the hoop. This length lets the bag loop over the rim and prevents the escape of insects while sweeping. An ideal material for making the bag is nylon mosquito netting, available from surplus stores. A good quality marquisette or similar material also can be used, but cotton mosquito netting or cheesecloth is not satisfactory.
To construct the net bag, cut out a piece of net material the size and shape shown in Figure 2. The bag may be placed on the wire loop before it is attached to the handle, or it may be sewn to the loop after it is attached.
It is advisable to sew a muslin or denim band over the loop to increase the durability of the net. Use a strip of heavy muslin or denim 5 x 44 inches. Fold it lengthwise to form a hem around the top of the bag (see Figure 3). The top edge of the net should be placed between the two sides of the folded muslin. Tuck the cut edges of the muslin so that the edge of the net and the tucked edges of the muslin overlap at least 1/2-inch. Join these by twice sewing completely around the material near the middle of the overlap.
When choosing a handle, select a strong, lightweight wooden dowel approximately 3 feet long. A 3/4-inch dowel rod is ideal for this purpose. Cut two grooves along the sides at one end as shown in Figure 4. These grooves cradle the bent arms of the hoop and are cut as deep as the thickness of the wire. Make one groove approximately 3 1/2-inches long and the other 2 1/2-inches. At the end of each groove, drill a small hole at a right angle into the handle to anchor the wire.
To make the loop, bend a 4-foot length of approximately 1/8-inch durable steel wire (preferably piano wire) into a hoop with short arms at each end as shown in Figure 5. Take care that the arms and the little hooks at their ends are bent correctly to fit along the grooves and into the holes in the handle. After fitting the hoop to the handle and properly attaching the bag, one is ready to make the joint fast between the handle and the hoop.
Wrap the joint tightly with fine wire (Figure 4), or better still, fit the handle with a sliding metal sleeve. A short piece of 3/4-inch copper or aluminum tubing fits snugly over a dowel rod of that diameter.
Handling insects properly can protect against possible bites or stings, as well as prevent damage to the fragile specimens. It is best to carry a pair of forceps (specialized tweezers, 4 to 5 inches long, Figure 6) to handle butterflies, moths, and other delicate and small insects. Fine-pointed tips allow you to handle even very tiny insects. To prevent losing or misplacing forceps and to keep them handy, attach them to a loop of string or yarn and wear them around your neck. Handle very small insects with a small paintbrush.
Left to thrash around in a net or killing jar, butterflies and moths often break wing tips or rub the scales from their wings, ruining the specimen. This can be prevented by immobilizing the insect immediately after you catch it. Through the cloth of the insect net, grasp the body of the moth or butterfly with wings up. Squeeze the sides of the thorax quite vigorously with the thumb and forefinger for 2 to 3 seconds. This paralyzes the specimens temporarily so the net can be opened and the specimen lifted out without danger of damage or escape. With a little experience, one learns to apply sufficient pressure to paralyze the insect without squashing it.
Avoid touching the wings of butterflies or moths with fingers unless it is absolutely necessary. Scales that provide the color patterns and the beauty of a moth or butterfly rub off very easily when handled leaving a less-than-perfect specimen for a collection.
Insects collected near home can be killed quickly and safely by transferring them to small bottles or boxes and placing them in a freezer for 1 to 3 hours. In addition to not having to worry about killing jars, one major advantage to this method is that the insects may be stored in a freezer for extended periods of time without the risk of the specimens drying out or decomposing until the collector is ready to mount them.
A killing jar also may be used for killing collected insects. Most collectors like to have at least two such jars - one large enough for butterflies and moths and another for beetles and other small insects.
To make a killing jar at home, select a heavy glass jar (1 pint to 1 quart in size) with a large mouth and a screw cap (Figure 7). Do not use plastic jars. Pour approximately 1 inch of wet plaster of Paris (more for larger jars) into the bottom of the jar. Let it harden, then thoroughly dry the jar in an oven set on warm. After removing it from the oven, saturate the dry plaster of Paris with ethyl acetate (available in many drug stores) and pour off any excess liquid that does not immediately soak in. Put the screw cap on the jar. Place a prominent label on the jar: "POISON - ETHYL ACETATE." The jar is now ready for use. Keep the jar tightly capped when not in use to extend the effectiveness of the ethyl acetate. When the jar loses its killing strength, dry it out and recharge it (re-saturate with ethyl acetate).
Always keep a piece of clean, crumpled paper toweling or facial tissue in each jar to absorb moisture and keep the specimens from being damaged. An experienced insect collector makes it a habit to mount and label all specimens within a few hours after they are caught. Insects left in the killing jar for more than a day become too soft and, thus, ruined, and those taken out but not soon pinned become too brittle to handle. With experience, a collector will learn to leave specimens in the jar long enough to make sure they are dead, but not long enough to ruin them.
Do not waste time putting damaged or mutilated specimens in the killing jar. Most insects are so plentiful that there is no reason to spend time and energy trying to mount and label less-than-perfect specimens.
A supply of small plastic or glass containers or vials comes in handy, especially on long collecting trips. Empty pill bottles are good for this purpose. They serve as temporary storage, so that large numbers of specimens can be collected without crowding the killing jars. Soft tissue or cotton placed in these containers cushions delicate specimens and prevents breakage.
After they have died, butterflies, moths, dragonflies, and other large-winged insects are protected best by removing them from the jars and carefully placing each specimen in an individual envelope or in a rectangular piece of paper folded to form a three-cornered envelope (Figure 8). Cut a regular piece of paper approximately twice as long as wide (3 in. X 6 in. is recommended for most butterflies and moths). Fold diagonally as on line (A), approximately 1/2 in. from the upper right to lower left corners. Fold the wings of butterflies and moths above their back to prevent scales from being rubbed off the upper surface of their wings and place inside envelope (B). Fold tabs to close off the open sides of the envelope. The envelope is then locked closed by folding over tabs (C). Write collecting data on the outside of the envelope.
Warm, cloudy, sultry nights in the summer offer the best conditions to collect moths, beetles, and other insects attracted to lights. Many aquatic insects also are attracted to lights near lakes and streams. Visiting porch, street, and landscape lights in the evening can yield many insects that are otherwise difficult to find. You can also use specialized portable lights to attract insects. For example, a gas- or battery-powered camp lantern placed in the middle of a white bed sheet may attract a large number of insects at night. Commercially constructed light traps are available from entomological supply houses, but effective traps also can be made at home (Figure 9). Lights afford good collecting throughout the spring, summer, and fall because various species occur at different times during the season.
Some insects are attracted to various food sources. Some can be collected from sweetened baits; others come to protein-based foods. Decaying meat attracts many beetles that can be trapped if the bait is placed in a glass jar or funnel trap (Figure 10) sunk into the soil with the opening flush to the ground surface.
Collecting aquatic insects can be very exciting and productive. First-time aquatic insect collectors are amazed by the number of insects in aquatic systems. Many insects are found by turning over logs and stones on the bottoms of shallow ponds and streams. To collect fast-swimming specimens, it is usually necessary to use some type of net. You can buy specialized aquatic nets, but a large tea strainer is adequate for collecting along the shallow margins of both ponds and streams. For collecting in faster waters of rivers and streams, a specially constructed device called a kick screen (Figure 11A) is the standard piece of equipment. The screen is placed in the current. Rocks immediately upstream from the net are then turned over, and the dislodged insects drift into and are caught on the screen. Commercially constructed, heavy-duty dip nets (Figure 11B) with long, sturdy handles are useful for collecting from deeper waters of lakes and ponds. Never use your aerial or sweep net to collect in the water, as it is easily ruined.
Careful attention is needed to collect insects from leaf litter and soil debris, because some of the specimens are very small and easily overlooked. Some collectors place soil litter on a white cloth or paper to make them easier to see and collect the insects as they attempt to crawl away.
Small trees and shrubs may be jarred or shaken, and the insects collected as they fall into an inverted umbrella or a light-colored beat sheet held under a branch or tree. This method is especially effective for collecting insects that "play possum" when disturbed. Figure 12 provides general guidelines of how to build your own beat sheet.
Every insect collector needs a good pocketknife. Pocket knives have a myriad of uses, such as removing bark from trees or borers from fallen logs or stumps; cutting off twigs; opening seeds, galls, fruits and vegetables; or even cutting into sod or soil. A trowel comes in handy to dig in the ground or leaf litter for larvae, pupae, and adult insects living there.
Last but not least, the collector should always carry a pencil and notebook for jotting down the place, date, collector's name and other important facts about the specimens collected. These data are important to include with any insect in a collection.
Many collectors prefer to carry field equipment, such as killing jars, note pads, vials, forceps, and brushes, in a backpack.
Although many insects are easily found, certain kinds live in obscure and unusual places. Discovering where, when, and how to search adds greatly to the challenge as well as to the productivity of an insect-collecting trip.
During summer, insects are plentiful on flowers and foliage of growing plants, in and around ponds and streams, beneath decaying logs or the bark of dead trees, around bright lights in the evening, and on the ground among grasses and weeds. Some insects come out only at certain times of the day or night, others only at specific times of the year. Some are found only on or near plants upon which they feed.
The bodies of dead animals often attract many unusual insect specimens (e.g., scavenger beetles) that are not likely to be found elsewhere. The same is true of the droppings of livestock, where specialized insects are apt to be found. With a little experience, the collector soon learns where to look for the less common specimens.
During winter, most insects seek shelter and are found in clumps of grass, beneath the loose bark of trees, under stones and logs, or beneath leaves and soil debris. Many burrow into the ground to pass the winter. Although insects are more difficult to find during the winter, searching for them is nonetheless interesting.
Insect collectors soon become very familiar with the behavior and habitats of insects they collect. They not only know where to look, but also what life stages are apt to be present. When a strange-looking caterpillar, beetle grub, or bug nymph is found, or when an odd-appearing larva is seined from the bottom of a pond, or even a mass of tiny insect eggs is found, it is only natural for the collector to wonder what the insect is and what it might look like as an adult when its life cycle is complete. These questions can be answered by rearing the insects.
To rear insects and observe them as they pass through their various stages of development helps the collector more easily recognize the insects. Rearing insects also adds to the pleasure of collecting and studying them. Some collection or display-box rules mandate that only the adult-stage insect may be included. Rearing an insect from the immature stage to the adult stage is not only educational, but also results in a nice addition to the collection.
Many kinds of rearing cages are used, most of which are constructed of screen to prevent escape of the adults as they emerge. Most insects are easy to rear, if you give them an environment similar to the one in which they were found. For example, to rear a caterpillar found on oak leaves, regularly add fresh oak leaves for it to eat until it pupates. Unless you are familiar with the habits of the insect being reared, it is best to always provide a few inches of soil in the bottom of the rearing cage because many insects need soil in which to transform.
Rear aquatic insects by placing them in an aquarium with the proper environment. As with fish, the water must be properly aerated. Aquaria and air pumps are purchased from pet supply stores. Aquatic insects also need access to the kind of food on which they naturally feed, such as tiny aquatic plants or other organisms.
An alert collector finds many insect specimens from very diverse habitats. For example, dragonflies, damselflies, and other aquatic insects are found near water. These, as well as other flying insects, can be captured by netting them in the air. Other insects such as nectar feeders (bees, wasps, butterflies, and others) as well as a myriad of plant feeders are best collected with the net as they rest on plants. These insects are collected by sweeping weeds, grass, or any other foliage with the collecting net - swinging the net back and forth, scraping the foliage with each pass as you walk along. After several vigorous sweeps, grasp the bag with your free hand or flip the net over the wire loop (Figure 13) to prevent escape of the specimens.
Most insects can be simply picked out of the net by hand, with forceps, or with a small brush, and dropped in a collecting container. However, a few, such as bees and wasps, may inflict a painful bite or sting if handled. To kill these and other small flying insects that readily escape the net, first briskly sweep the net through the air to force the insects to the bottom of the net, then place the portion of the net containing the insects in the killing jar. Place the lid on the jar for a few minutes until the insects become lifeless. Once immobilized, they may be safely dumped directly from the net into the killing jar without danger of them stinging or escaping.