Identification guide to the ant (Hymenoptera: Formicidae) genera of the Midwest of the USA

Introduction and how to use the keys

How to prepare specimens

Image-based identification guide

Introduction and how to use the keys

     This image-based identification guide should enable the user to identify any ant collected in the Midwest to the genus level. All keys used in this identification guide are modified from one or more sources (e.g. Creighton 1950, Wheeler & Wheeler 1963, 1986, Holldobler & Wilson 1990, Bolton 1994, see the literature cited for complete list)

     The keys used in the guide are dichotomous. At every point, the user must decide which of two statements (together forming a couplet) best describes the specimen being examined. If the correct decisions are made, the key will lead through couplets to the correct identification.

     For example, the first couplet for the key to the genera of the subfamily Myrmicinae looks like:
1.Antennae with ten or less segments (Fig. 55). ...2.
    Antennae with more than ten segments (Fig. 56). ...3.

     If the ant being examined has 10 or less antennal segments, you would follow the link to couplet 2. If the ant is blessed with 11 or more antennal segments, then you would follow the link to couplet 3. Whenever possible, images showing the characters used in the key are displayed in the top half of the page. So, in the example above Figure 55 shows a 10 segmented antenna and Figure 56 shows an 11 segmented antenna. A list of the taxa remaining in the key (all 17 of the Myrmicine genera found in the Midwest in the example above) is shown to the left so that the user has some idea what possibilities are left.

     In some cases, more than one diagnostic separatory character is presented in the couplets. The first character is generally the most useful or easily seen. No specimen should fit both halves (or 'lugs') of the couplet - the characters used in keys are supposed to easily and efficiently separate the taxa for which the keys are made. If you cannot make a clearcut decision (as is often the case, especially when the keys are unfamiliar), proceed through each of the two paths until you reach an endpoint. Hopefully it will be obvious (from the characters used in the key and from the available images) which of the two possible identities is correct.

     As an identification aide, when a taxa is reached in the keys, the Midwestern states in which the taxa has been collected are reported in parentheses directly below each lug. For example, couplet 11 of the key to the genera of the subfamily Myrmicinae looks like:
11.Propodeum armed with spines.
(collected in all Midwestern states)
   Propodeum not armed with spines.
(one species, M. mutica, collected in western North Dakota)

     So, if you got to couplet 11 and for some reason you were unsure whether your specimen had spines, you could be nearly certain that you had a species of Myrmica unless you collected your specimen in western North Dakota (or outside of the Midwest).

     As a further aide, taxa which are very rare (defined as having been collected in 5 or less counties throughout the Midwestern states surveyed) are marked with a pound symbol (#). Similarly, taxa which have been collected in 6-11 counties are marked with a double-pound symbol (##). Taxa marked as such are unlikely to be found with casual collecting and much of the time you can safely skip over these taxa.

     And finally, because the focus of the present study has been on the ants of Minnesota, ant taxa which have not been collected in Minnesota are marked with an asterisk (*).

     After specimens are identified to the genus level it becomes necessary to use keys found in the literature for each species group and genus. MacKay and Vinson (1989) give an annotated list of references needed to key Nearctic ants to the species level. Also see the literature cited for sources used to identify Midwestern ants. Note that a few notes and revisions have been completed since MacKay and Vinson's 1989 guide: the generic relationships of Dolichoderinae (Shattuck 1992a,b, 1995), Dolichoderus (MacKay 1993b), the Aphaenogaster fulva-rudis-texana complex (Umphrey 1996), genera of the tribe Dacetonini (Bolton 1999), and the Leptothorax Myrafant subgenus (MacKay 2000).

Please send any questions or comments regarding these pages to Tim Linksvayer (
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