General information about collecting insects and arthropods
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Most general text books and field guides covering the study of insects provide general guidelines for collecting and preserving specimens such as those found in A Field Guide to Common Texas Insects (Drees and Jackman, 1998; see Appendix A, Collecting and Preserving Insects), Bagging Big Bugs (Cranshaw and Kondratieff 1995), A Field Guide to the Insects (Borror and White 1970) or other references. However, each group and in some cases, each species, may require unique methods for study.
There are certain tips to finding specimens to collect. Seasoned collectors can often journey directly to a particular habitat location at a particular time of the year, look as a specific host plant and almost always collect a few specimens of often rare species. They understand that populations thrive and survive year after year under favorable conditions, repeatedly and predictably rotation through their life cycles. Understanding the biology of the “target” species is the first step to finding it to collect:
• Habitat: Knowing the habitat(s) and the host plants or food on which insect species develop will narrow you search. One of the most predictable places to collect insects is in agricultural fields, assuming they have not recently been sprayed with an insecticide. For instance, in soybean fields using a sweep net or drop cloth, one can almost always find a select number of insects including caterpillars, stink bugs and a variety of natural enemies. If you want to collect an alfalfa weevil, find an alfalfa field!
• Seasonality: Most insects develop through the year. Knowing when the stage you want to collect occurs, such as the adult stage, will allow you the focus collecting during particular weeks or months. In the winter, for instance, insects can still be found, but in whatever stage they spend the winter months. For example, June beetles and May beetles overwinter as partially developed C-shaped grub stages in soil of turf grass.
• Collection equipment and methods: Once you are in the right place at the right time, know what to look for and how to capture it. Because of behavioral differences between species, some can be caught in a jar while fast moving or flying insects require another approach. Similarly, because these arthropods vary so greatly in size from mites and parasitic wasps the size of microscopic specs to walkingsticks and the black witch moth that measure 6 to 8 inches, different techniques need to be used to collect them.
• Preservation: Methods for killing and preserving specimens varies by insect group, as well as life stage. Most hard-bodied stages are killed in a killing jar or frozen before being mounted on a pin for display in a collection box. Over periods of years, dry brittle specimens are vulnerable to color fading if exposed to sunlight and attacks by book lice or dermestid (carpet) beetles if kept in a dark place and/or without chemical protection such as the fumigant paradichlorobenzene (PDB), the repellent napthaline in moth balls, or fumigating pest strips containing dichlorvos (DDVP). Soft-bodied insects and immature stages are usually killed and preserved in some type of fluid such as rubbing alcohol or a special preservative fluid, sometimes after first being boiled in water, and are stored in vials. Keeping vials filled with alcohol over a period of years is difficult due to evaporation or leaks requiring periodic inspection and re-filling. Specimens of tiny arthropods like mites and thrips are usually mounted on microscope slides for study.