THE CLASSIFICATION OF INSECTS
Estimating a PMI requires that the forensic entomologist be able to precisely identify the insects on and around a body. This can only be properly performed by an experienced forensic entomologist with the proper reference collections. Differentiating between closely related insects, especially certain species of flies, requires the recognition of minute anatomical details and should be attempted only by qualified professionals. The science of identifying and classifying organisms is called taxonomy. All organisms are categorized by their relatedness through the recognition of significant evolutionary traits. The order of relatedness is broken into these taxa, or related groups: Kingdom, Phylum, Class, Order, Family, Genus, and Species.1 When we refer to a specific type of organism, describing it by the genus and species (and sometime subspecies) is sufficient to set it apart from all other organisms. Thus, when talking about Calliphora vicina, Canis familiaris, or Homo sapiens, we know we’re discussing the blue-bottle fly, the domesticated dog, and humans. These terms are formal so the genus is capitalized and, because they are Latin, it is proper to format genus and species designations in italics. Some species, especially among insects, have well-defined variants or subspecies. A taxonomic key is a method for classifying organisms where each trait identified separates otherwise similar groups of organisms. By following a detailed key, a forensic entomologist can identify, or “key out,” all of the forensically important insects that may be found on or around a body (see Table 9.1).
