IMMATURE INSECTS

Collecting Immature Insects

Collecting immature insects will help you learn more about the life cycle of the insects. Immature insects occur in many of the same places as adult insects. Some are easier to find and collect. Others may be hidden in logs, plant stems, soil, pond silt, manure and other messy places. You may need an axe, knife, trowel, sieve or tweezers depending on the habitat (living niche) you are going to search. You will also need a note pad, pencil and a supply of jars with lids numbered with a china pencil or stick-on label.

You will probably find many larvae of the same kind living together in groups or in the same habitat niche. Or you may find a variety of larvae living close together. Collect five or six larva of each kind. Use a separate jar for each kind, and add to the jar some of the material in which you found the larvae. This will keep them alive and fresh until you get home and can prepare them for preservation. Do not mix different larvae together or overcrowd larvae in the same jar. They may injure each other if they are overcrowded or are of different kinds.

Record information on your note pad that will be useful later when you are making out permanent labels or identifying the larvae. Record the following notes for each jar:

Some insects will stay alive in collecting jars for several days or more. Others may die and begin to rot in a few hours. Be ready to preserve soft-bodied larvae as soon as you get home.


Preserving Immature Insects

Insect nymphs can be placed directly into alcohol for storage, but insect larvae may shrivel up in alcohol unless they are "fixed" first. There are special fixative solutions you can buy from biological supply houses, but you can easily fix insect larvae with a hot water treatment. To fix insect larvae with hot water, bring a cup of water to a boil in a sauce pan. Remove the pan from the heat and wait a half minute. Then pour the hot water onto the larvae you have waiting in a coffee can. The larvae will be killed instantly, but they should be left in the hot water for several minutes until they are slightly cooked. If the water is too hot when you pour it on the larvae, they may burst open like an overdone wiener. If the water is not hot enough, it may not kill the larvae instantly and they will also be underfixed. After the larvae are fixed, transfer them to 70% alcohol in glass vials with a tight-fitting cap or a stopper.

Prepare an information label to go into each vial of immature insects. Tell the date and the location where the insects were collected. Also tell on what plant, animal or other habitat they were found, who collected them and how they were prepared for storage (see the example). Use high quality rag paper for the label or else it may dissolve in time. Use India ink and a fine crow quill pen or a No. 2 pencil to write out the label. Labels written with ball point pen, hard-leaded pencil or a typewriter will fade and become unreadable. When you find out what kind of larvae you have, you can add an identification label to the vial. Do not attach labels to the outside of the vials. They will eventually rub off or get smudged and unreadable.


Identifying Immature Insects

Identifying immature insects in a systematic way with keys is very difficult without a good microscope and special training. However, there are other ways to identify common types. Some larvae are very distinctive in appearance; some are found in special places. They are often illustrated in the same books you use to identify adult insects. Social insects occur in all stages in their colonies; by identifying the adults you know what the larvae are. Some nymphs resemble the adult form so closely that you can associate them with their adults very easily. Rearing immature insects to the adult stage is another way to identify the immature form. The following notes may be helpful for identifying some immature insects.

Insect Nymphs
Caterpillars
Beetle Larvae
Hymenoptera Larvae
Diptera Larvae