The Class Arthropoda, which includes insects, spiders, mites, and their relatives, is without question the most successful group of organisms on the planet. Insects alone account for nearly 55% of all species known to science (Barrowclough 1992). Spiders, mites and insects inhabit every terrestrial habitat on the planet and play a major role in the evolution and maintenance of biotic communities. They are the primary pollinators of flowering plants; they are important consumers and recyclers of decaying organic matter; and they are integral components in the foodwebs of vertebrates and other invertebrates. For these reasons, and many others, the study of insects and their relatives is of increasing importance as society faces increased challenges to preserve and enhance environmental quality, reduce pesticide usage, increase crop productivity, control food costs, and increase trade in the global community. Pest species are responsible for enormous economic losses annually, attacking crops and ornamental plants, causing damage to our food and clothing, and vectoring diseases that effect cultivated plants, our pets and livestock, and ourselves. The damage cause by pests species is far outweighed by the positive effects of beneficial species. Pollinators ensure the production of fruit, parasitoids and predators help control pest species, some species contain chemicals of pharmaceutical value, and a large number of species contribute to the decomposition and recycling of dead and decaying matter.
Because of the damage inflicted by pest species, increased knowledge of these organisms has the potential to save lives and money. Correct identification of a newly detected pest or disease vector is of utmost importance because the scientific name of an organism is the key to all known information about its morphology, its behavior and life history, and its potential threat to human welfare.
The behavior of insects and mites can be observed most easily in their natural environments. However, many species, especially the smaller ones, must be collected and properly preserved before they can be identified. Because correct identification seldom is easy, it is important that specimens be preserved in the best condition possible. The identification of a particular insect or mite usually requires examination of minute details of its anatomy with the aid of a hand lens or microscope. Some specimens may require dissection or even study with the electron microscope. If these details on a specimen are concealed, missing, or destroyed because of improper handling or preservation, identification is made difficult or impossible, and information about the species to which it belongs cannot be made available. Therefore, adequate preservation and proper labeling of specimens are essential to their identification.
The methods used to collect insects and mites are dictated by the ultimate goal of the samples collected. Insects may be collected as a hobby for personal enjoyment of their diversity and beauty. They may be collected in conjunction with school courses on biology or entomology. Specific insects groups may be sampled to assess or measure biodiversity to help identify appropriate areas to be included in reserves. Aquatic species may be used to detect changes in water quality. Pest species may be sampled to assess presence/absence or abundance in order to determine whether control measures are necessary. Specific groups or species may be collected to acquire material for biological, physiological, ecological, molecular, and systematic studies.
This manual provides a summary of the methods and techniques used by professionals and amateurs alike to collect and preserve specimens for study. While many of the methods covered here, such as pinning, have changed very little in the last hundred years, other techniques have become available only in the last few years or decades with advancing technologies. Older manuals such as Steyskal et al. (1986), Martin (1977) and Upton (1991) while still useful will not cover such these as preservation for molecular studies. In addition, most of these older publications are now out of print and may be difficult to find.
Because of their incredible diversity, insects, mites, and other related groups vary widely as to their proper collecting requirements and methods. In the following sections, we will explore some of the many recommended techniques and look at the varied equipment used by collectors. The emphasis will be on insects and mites, but much of what is included here will also pertain to other related groups such as spiders.
Which species and how many specimens to collect depends on the purpose for which the material is intended. For hobbyists and students, small samples are usually adequate. However, when important pest insects and mites need to be identified, they should be collected in series if at all feasible. A sample of 20 specimens should be considered the minimum, and even larger numbers may be desirable. If adults and immatures are present, specimens should be collected of all life stages. Excess specimens can be discarded or exchanged, but it is not always possible to collect additional specimens when needed. Frequently insects and mites cannot be identified accurately from immature stages, and it is then necessary to rear them to the adult stage to obtain a precise identification. Photographers should collect the specimens they photograph if positive identification is desired; minute, critical diagnostic characters often are not depicted in photographs. If specimens are destined for display cases that portray them in their natural habitats, it may be important to collect a sample of the host plant for the display.
Many persons starting a collection attempt to collect every specimen they find. Biology students in high school and college are often required to collect specimens from as many orders or groups as possible. The experience and knowledge gained in making a general collection are of value in helping the collector decide on a specialty. However, with so many different kinds of insects from which to choose-over 100,000 described species in North America alone-most persons find that as their skills and interests increase, concentrating eventually on 1 or 2 of the major insect or mite groups is desirable. Specimens other than those in a chosen group may still be collected for exchange with other collectors.
References: Lewis & Taylor 1965; Seber 1973; Barrowclough 1992.
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