STRUCTURE OF THE KEY

These keys are dichotomous for the most part (nearly always only two choices offered) and, as much as possible, field and laboratory oriented (called an "artificial" key by biologists). That is, we do not feel obligated to build these keys along phylogenetic lines (which would be a "natural" key), although it is usually helpful (often necessary) to consider the defined characteristics of a taxon in sorting out similar species. Unfortunately, criteria important for distinguishing higher taxa are seldom useful for identifying specimens in the hand (Gosner, 1971). An excellent source of information on organism phylogeny is provided at the The Tree of Life web site.

These keys cannot take into account groups or species which are not found in Hawai`i or are not somehow associated with aquatic environments, although the early couplets should work elsewhere. Note that these "preliminary" couplets are purposely non-technical and intended for students who may not have much training in biology. Experienced biologists and naturalists are expected to skip ahead (using the Index page) and enter the keys beginning at the appropriate place considering the knowledge they already posses of the specimen they are attempting to identify. It is an unavoidable fact that keys become more technical as the identification process progresses as necessary to achieve an accurate determination.

Descriptions of characters, in lengthy choice descriptions, proceed from most critical to least critical (to the extent that this can be assessed). This is not the same as from characters easiest to observe to most difficult to observe. Users of the keys must guard against a tendency to put undo importance on those characters easily observed, ignoring characters not so easily seen. Also, careful attention must be paid to the wording of each description. The word "OR" is used to indicate that any one of two or more descriptions may fit, whereas the word "AND" indicates that all characters must fit. The word "usually" indicates a character which is expected to fit (true in most common specimens), but need not be true.

Within some couplets, particularly those describing a species, the bracket { symbol is used to separate information preceeding that is critical to an accurate identification from information following the bracket that is useful, but not necessarily unique to that species or taxon (for example, size and habitat preference). It is important to understand that the complete description of a species is not just what appears in the couplet bearing the species name but in the sum of characters from all of the couplets leading up to that species. Skipping over couplets can lead to unrecognized errors in identification.

It is not possible to fully use these keys without magnification aids (microscope, hand lens). Many important characters are simply too small to observe with the unaided eye, especially on small creatures. Further, it may be necessary to accomplish these observations by collecting specimens, which some students and naturalists may be reluctant to do. For this reason, partial identifications are offered along the way. These will usually be group names (a taxon above the genus). Stopping at a group name can provide a satisfactory conclusion and may still be useful in understanding the ecology of a body of water. Partial identification may form the basis for verification with picture aids ("collecting" by digital camera is a rewarding approach) or a knowledge of species distribution. For example, if the choice between 3 or 5 teeth on the mandible cannot be determined without careful dissection under a powerful (yet unavailable) microscope, and it is learned that one species is limited to pools in caves and the other common to urban streams, the collection location could clinch the identification.

A large ziplock bag or plastic bottle can be used for observation of small aquatic animals caught with a net and temporarily held in the field. Specimens collected and placed in an aquarium in the laboratory or classroom should not be returned to the same or another aquatic environment unless competently identified as a native species. In the keys, native species are marked by one of the following: [IND], meaning indigenous -- native to Hawai'i but found elsewhere on other Pacific islands; or [END], meaning endemic -- native to Hawai`i and found naturally no where else in the world. Species believed to have been brought to Hawai`i by the aboriginal human inhabitants are marked as Polynesian introductions [POL]. All other species are non-native, for which terms such as "naturalized", "alien", or "introduced" would apply.

This "under construction" sign is a warning that the couplets in that part of the key are still being developed and caution should be used. Some choices given may not go anywhere because the keys are incomplete, or the choices may not be constructed very well. The Index page provides a listing of keys developed and keys under construction.