7 November 2021 note: It looks like the free version of Lucid is no longer available. I posted a new version of the lucid files below, and an updated .csv with the data.
The genus Pheidole in the New World contains hundreds of species, and identifying them based on external morphology is no easy task. Traditional dichotomous keys are frustrating because so many steps are needed and most characters are continuously variable across the genus. I provide here a set of downloadable files that can help in the identification of the extant New World species.
Although not a part of this website, there is also an extensive description of Pheidole characters by Katsuyuki Eguchi. It is an excellent general guide to characters important for species distinctions in Pheidole. Eguchi made this document as part of the ANeT Ant Course held in Malaysia in 2005. The document can be viewed and downloaded here. It is designed for Indo-Malayan species but works very well for New World species too.
The files on this website are designed to be used with Lucid, which is commercial key-making software. Lucid uses a matrix key approach, in which one window shows characters and another window shows available species. As character data are entered (in any order), species that do not satisfy the criteria are dropped from the list. Characters can be entered until a suitably restricted list is obtained. The goal of the key is to provide a relatively small set of characters that can trim a list to a manageable size. The species can then be looked up in other resources such as AntWeb, or Wilson's 2003 revision of the New World species, or Piotr Naskrecki's CD of Pheidole images that accompanied Wilson's revision. I have found that a basic set of 6 measurements is remarkably useful for narrowing a search. The measurements are head length, head width, and scape length of both the minor worker and the major worker.
Several years ago I started a "Pheidole working group" site, that contained many of the same resources presented here. That site is no longer being updated, but a more or less moth-balled version of the site is available here. The site had a deployed Lucid key. But it has become problematic to actually deploy Lucid keys on the Web, due to changes in browser security settings. Lucid has offered an old version of its software as a free download. My work-around is to have users download the free version of Lucid and import my Lucid key. Users can then use the key as a stand-alone application.
The following files are provided in a single zipped file:
Pheidole20210104.lk4 The Lucid file that can be opened in Lucid 3.3. Launch Lucid3Player and open this file. If you want to modify your own copy, you can open in Lucid3Builder.
Pheidole20210104 A folder that accompanies the key and must be in the same folder as the .lk4 file.
PheidoleCharSet20210104.pdf This file lists the characters as they appear in the Lucid key and provides definitions, explanatory information, and figures.
PheidoleMatrix_20210104.csv A file suitable for import into Lucid. This file contains the full species x character matrix.
If you find errors or have suggestions, contact me at jacklongino@gmail.com.