Part 5

Collecting Larvae.--Practically every stream or lake has some aquatic insect larvae which may be collected by various methods, some simple and others requiring specialized and complicated apparatus. For general collecting, the following suggestions may be of value:

1. Look under logs and stones. Search out crevices in them; some insects hide away and demand of the collector a keen and careful search.

2. Tear apart bunches of leaves, roots, and other debris that may have piled up in front of a rock or log, or that may have accumulated at the end of a root or branch dangling in the water.

3. Pick out bunches of aquatic plants and search through them carefully.

4. Sift mud, sand, or gravel taken from the bottom of a lake or stream. Remember that some insects build cases in which they hide when disturbed. It takes a practiced eye to see a motionless case. After an insect has dried out a little, it partially emerges from the case and drags it along in search of water; moving in this way, it is easy to see.

HOW TO HANDLE UNMOUNTED SPECIMENS

Soon after insects are killed they dry out, become very brittle, and are damaged easily. Small, fragile insects especially are susceptible to breakage and, when dry, break up readily into fragments. Hard-shelled insects, such as beetles, may appear to be sufficiently durable to withstand handling when dry, but even these insects have fragile legs, antennae, and other parts which snap off readily when handled dry. Newly killed material should be either mounted or put in temporary storage before it has dried out. If collected material dries out before it can be mounted or stored, it should be relaxed by special techniques so that the specimens can again be handled without danger of breakage.

Temporary Cases

If it is not convenient to mount the specimens when they are taken from the killing bottle, the moths and butterflies should be put in papers and other insects in cellucotton.

Papers are simply rectangular strips of paper of convenient size folded as in fig. 9. A moth or butterfly, with its wings folded, is placed in a paper, the edges of which are then crimped over to lock it shut.

For insects other than moths or butterflies, cardboard pillboxes containing cellucotton make good temporary housing, fig. 10. A layer of cellucotton is laid in the bottom, a layer of insects placed on it, and another layer of cellucotton placed over the insects. The lid should fit fairly snugly over all. Cigar boxes and other boxes of like size also may be used in the same way.

Great care must be taken that sufficient cellucotton is put in the box to take up all moisture in the insect bodies. If the specimens are large, they should be allowed to dry moderately uncovered before being placed in cellucotton in storage containers. If insects become damp in the containers they quickly mold or rot. The containers should be wood or cardboard boxes, for they will not sweat, as will a metal box. The insects should be packed tightly enough to prevent their rolling around and breaking.

Relaxing Boxes and Jars

At any desired time the dry specimens may be relaxed and mounted. A relaxing box or jar is easily made. In the bottom of a wide-mouthed jar with a screw-on lid, put an inch or two of clean sand; saturate the sand with water containing a small amount of phenol (carbolic acid) and place over it a piece of cork, cardboard, or wood cut to fit the jar. Place the dry specimens on the cork or other material, and cover the jar tightly with the screw-on lid. The lid must be practically airtight. In a day or two the specimens will be soft and pliable enough for pinning or spreading, the next steps toward permanent arrangement of the collection.

The relaxer will sweat if kept in too hot a room and will spoil the specimens. Also, the insects will be spoiled if left in the relaxer too long. The correct length of time varies with each relaxer and can be learned only by experience.

HOW TO MOUNT AND PRESERVE SPECIMENS

Most adult insects in collections are mounted on pins. Most medium-sized to large insects, such as grasshoppers, butterflies, moths, flies, bees, and many beetles should be pinned directly through the body from top to bottom. Many small insects, such as leafhoppers, plant bugs, small beetles, and the like, should be glued on card points. Immature insects and the adults of some groups are best preserved in fluid.

Preservation by Pinning

Hard-bodied insects, such as beetles, flies, and wasps, are preserved as dry specimens on pins better than in fluid. The pinned specimens are more convenient to study and they retain their natural coloring better. Flies and butterflies are covered with hairs or scales that clot or break off if the specimens are preserved in fluid, and for this reason they should be pinned.

Common household pins are too thick and short for pinning insects. Longer, slender pins called insect pins are necessary and may be purchased from various supply houses. They should be of spring steel; a brass pin will corrode and be destroyed by acids in the insect's body. The pins are available in numbered sizes, of which 1, 2, 3, and 4 will be found of most general use, and sizes 0 and 00 of advantage in special cases.

Medium to Large Insects.--Medium to large hard-shelled insects such as moths, beetles, flies, bees, and wasps, should be pinned vertically through the body, fig. 11a. It is essential that the pin pass through a fairly solid part of the body, and, to insure this, the following standard procedures should be adopted:

1. Bees, wasps, flies.--Pin through thorax between bases of front wings slightly to right of middle line, fig. 11b.

2. Stink bugs.--Pin just to right of middle line of the scutellum or large triangle between the bases of the front wings, fig. 11c.

3. Grasshoppers.--Pin through back part of prothorax (the saddle behind the head) just to right of middle line, fig. 11d.

4. Beetles.--Pin near front margin of right wing cover near middle line, fig. 11e.

5. Moths, butterflies, dragonflies, damselflies.--Pin through the center of the thorax between the bases of the front wings, fig. 12.

The insect should be pushed about three-quarters of the distance up the pin, but not so close to the top that no room is left for easy handling of the pin with the fingers. It is well to have all insects the same distance from the top of the pin. To insure a uniform distance, the collector should use a pinning block. This is a small piece of wood or metal usually in the form shown in fig. 13, into the top of which are drilled holes slightly larger than the pin diameters. Such a block may be fashioned of wood with holes made by small nails and covered with a cardboard rectangle through which have been stabbed holes the exact size of those in the wood. The depths of the holes in the block should be three-eighths inch, three-quarters inch, and 1-1/8 inches, respectively. To use the block, pin the insect and insert the pin into whichever hole allows the specimen to be pushed up the pin and still leave room, allowing for the thickness of the insect's body, for handling at the top.

Tiny Insects.--Very small insects should be mounted on card points or on minuten pins. Regular pins would break too many of the insects' body parts.