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How to Use the Keys

The identification keys used here are called dichotomous keys. A dichotomous key consists of a pair of differing statements (a couplet). The user must decide which of the pair best describes the ant (in this case) being examined. Each half of a couplet ends in either a number, which, when clicked, will lead to another couplet or it ends in a subfamily, genus, or species name. If the couplet ends in a subfamily name, click the subfamily name to go to genera keys in that subfamily. If the couplet ends in a genus name, click the genus name to go to the species key for that particular genus. Finally, if the couplet ends in a species name, click the species name to go to a page that gives more information about that species (this will be the case eventually anyway, all pages are not up yet). There are some cases in some of the generic keys where the couplet leads to a genus and species name rather than just a genus name that leads to a species key. In this case, there is only one species known or likely in this area and thus, it is simply keyed to species level at that point.

In many instances the couplets contain more than one character for separating the ants. Generally, the first character is the most useful character, however all characters should be looked at if possible. If, when running ants through a couplet, you have difficulty making a definitive decision, then continue through each part of the couplet until you have reached an endpoint. By doing this it usually will become obvious which of the two resulting taxa is correct based on the characters in the key and from any drawings or photographs provided.

All of the keys on this site are for workers unless otherwise stated. There are a few keys included for other castes at this time, but not for many groups. It is advisable to collect series of ants with as many castes as possible (workers, including majors and minors, if applicable; males; and queens-females). It is sometimes difficult, if not impossible, to identify some species from a single specimen. There is much variation in ants and it is best to look at series of individuals whenever possible. Often, the only way to identify males or females, is by association with nest series. Queens, sometimes may be run through the workers with success, but this is never the case with the males, which are generally quite different in appearance from either the queen or workers.

The keys provided here are compiled from many sources including published papers on ant taxonomy, web sites concerning ant identification, personal observations, and information garnered from individuals working with specific groups of ants. Literature records and web sites are cited when used. These keys were put together by Joe MacGown and users should use them at their own risk! If any problems with the keys are seen, mistakes noticed, or if anyone has additional information on specific groups that would make these keys more useful, please feel free to contact Joe MacGown. As further information is gathered, the keys will be updated and photographs and drawings will be added as time permits. Hopefully, these keys will be of some use to those trying to identify ants in this area.

If there is difficulty understanding any of the terminology or names of structures, there are links on the side and bottom of every page to a Glossary of terms.

At times in the keys, various indices and measurements are used. These terms are described below (see the Morphological Measurements page on AntWiki for mor information and diagrams)

Measurements Used

EL - Maximum diameter of compound eye
FL -
Forefemur length
FW -
Forefemur width
longest length of forewing
- Length of gaster in dorsal view (not including acidopore, genitalia of males, or sting)
- Head length in full frontal view from anteriormost point of clypeus to a line perpendicular to the posteriormost point of head.
HW - Maximum width of head (including eyes) in full frontal view
MandL - The straight line length of the mandible at full closure, measured in the same plane for which the HL measurement is taken (i.e. full face view), from the mandibular apex to the anterior clypeal margin, or to the transverse line connecting the anterior-most points in those taxa where the margin is concave medially.
ML (WL) - Mesosomal length (Weber's length) from anterior edge of pronotum to posterior corner of metapleuron
PetNL: Maximum length of petiolar node, measured longitudinally from the level of the anterolateral angle/corner to that of the posterior-most extension of the petiolar tergum, where it surrounds the gastric articulation.
PetW - Maximum width of the petiolar node in dorsal view.
PnL: Pronotal length measured from the anterior edge of the pronotal collar to the pronotal-mesonotal suture parallel to the measuring axis.
PpL: Postpetiole Length. Measured from anterior to posterior inflections of postpetiole node in lateral view.
PpW: Postpetiole width measured as the maximum width of the postpetiole, in same view as and perpendicular to postpetiole length.
PronW (PW) - Maximum width of pronotum
PTH: Petiole Height. Measured from petiole sternum to apex in lateral view.
PTL: Petiole Length. Measured from anterior to posterior inflections of petiole node.
SL - Length of antennal scape from base (not including radical) to terminal point
SPL: Propodeal spine length measured from the tip of propodeal spine to the closest point on outer rim of the propodeal spiracle.
TL - HL + WL + GL


CI = Cephalic index, HW X 100/ HL
FI - Femur index, FL X 100/HL
OI = Ocular index, EL X 100/HL
REL - Relative eye length: EL/HL
REL2 - Relative eye length, using HW: EL/HW
SI = Scape index, SL X 100/HL