17.3.3. DNA-based identifications and voucher specimens
Insect DNA is acquired for population studies, to assist with species delimitation or for phylogenetic purposes and, as recently publicized, may be used for DNA-based identification in which the sequence of base pairs of one or more genes is used as the main criterion for recognizing species (called DNA barcoding).
The optimal preservation of insects for subsequent DNA extraction, amplification, and sequencing usually requires fresh specimens preserved and stored in a freezer at —80°C, or in absolute ethanol and refrigerated. It is essential that appropriate voucher specimens are retained and, if possible, most or part of the actual specimens from which the DNA is extracted. For example, DNA can be extracted from a single leg of larger insects or, for smaller insects, such as thrips and scale insects, there are methods for obtaining DNA from the whole specimen while retaining the relatively intact cuticle as the voucher.