Ants (Hymenoptera: Formicidae) of Alberta: A key to species
based primarily on the worker caste
CJAI 22 July 4, 2013
doi:10.3752/cjai.2013.22

James R.N. Glasier1, John H. Acorn2, Scott E. Nielsen2, and Heather Proctor3

1 Corresponding author: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1 jglasier@ualberta.ca
2 Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1 john.acorn@ales.ualberta.ca, scott.nielsen@ales.ualberta.ca
3 Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9 hproctor@ualberta.ca

| Abstract | Introduction | Materials | Discussion | Checklist | Glossary | Species Key | Acknowledgments | References | PDF (11MB) | Cite this Article |

Overview of the Fauna
Based on published records and the collections described above, there are 93 species (one of which includes two named subspecies) in 16 genera and three subfamilies known from Alberta (Table 1 and Figures 4-94).  By far the most species-rich genus is Formica, with 38 recorded species. Other species-rich genera include Camponotus, Lasius, Myrmica, and Leptothorax. Several rare or geographically restricted genera include Dolichoderus, Solenopsis, Manica, and Pogonomyrmex. There are four putatively endemic species in Alberta: Leptothorax athabasca Buschinger and Schulz, Leptothorax pochahontas (Buschinger), Leptothorax faberi Buschinger, and Temnothorax fragosus (Mackay and Buschinger), all apparently restricted to the Rocky Mountains. Of the 93 species of ants in Alberta, 91 are indigenous and two, Monomorium pharaonis (Linnaeus) and Brachymyrmex obscurior Forel, are introduced and are almost solely found within human buildings (Klotz et al. 2008).

Taxonomic Issues
Several genera likely contain more species in Alberta than are listed. Some may be undescribed, while others are simply difficult to distinguish and are thus not yet confirmed for the province. These issues are briefly summarized here.

Leptothorax: Leptothorax species are difficult to identify confidently, as the diagnostic characteristics for many species are poorly defined (Fischer and Cover 2007; Buschinger and Schultz 2008). Even among the species we chose to recognize here, many individuals will be difficult to place correctly. In addition, the taxon we refer to as Leptothorax muscorum (= “L. canadensis" (Nylander), a name proposed for North American members of this Holarctic taxon) may represent several species in Alberta, including L. pocahontas.

Temnothorax: like Leptothorax, Temnothorax from the northern Nearctic is relatively poorly known (Mackay and Buschinger 2002; Buschinger and Schultz 2008). It is possible there are more species waiting to be recognized in Alberta.

Myrmica: this genus contains several species that are morphologically similar (Fischer and Cover 2007). It is probable that because of limited taxonomic work, and limited collecting, more species exist in Alberta. Two potentially new species (referred to here as Myrmica ab01and Myrmica code AF-eva), are morphologically distinct from known species, and were included in the key as tentatively different until further descriptions can be made. Myrmica ab01 is similar to Myrmica crassirugis but possesses distinctly upturned propodeal spines. Myrmica code AF-eva is similar to Myrmica americana, but possesses smaller lamina on the basal bend of its scape. As the North American Myrmica are currently being revised by Dr. André Francoeur, at University of Quebec (personal communication), these potentially new species may be described by him.

Formica: the genus Formica contains six species groups and numerous species that are difficult to separate from one another (Fisher and Cover 2007). Traits that cannot be seen without a high resolution dissecting microscope, regional variation within species, and differences relying on subtle characters based on setae and/or pubescence often make Formica difficult to identify to species with any confidence. In this key we try to simplify these difficulties, but comparison with identified material, and familiarisation by working with large numbers of specimens is the best way to see the differences present between similar species of this genus. We recognize a difference between subspecies F. oreas oreas and F. oreas comptula; however, more work is needed before determining if they are conspecific, are indeed subspecies, or deserve further taxonomic separation. In addition some specialists informally suspect that F. obscuripes and F. planipilis may hybridize or be conspecific, though we chose to keep them separate for this key as they are well established in the literature (Creighton 1950; Wheeler and Wheeler 1963; Wheeler and Wheeler 1986; Mackay and Mackay 2002).

Preparing Specimens for Use with this Key
The key is intended to allow identification of worker-caste ant specimens from Alberta, but careful specimen preparation will facilitate identification. The following tips should ensure that adequate material is acquired at the time of collection. A stereo microscope with at least 50X magnification is required to see many of the characteristics mentioned in the key, and careful experimentation with lighting, including diffusion, may be required as well.

  • Collect a range of worker sizes and multiple specimens (minimum of five recommended).
  • Specimens in ethanol can be difficult to identify. It is best for the specimens to be pinned, pointed (glued to a triangular card) and dry, so that structures such as erect setae are easier to see.
  • When pointing specimens make sure the mandibles are open so you can see all mandibular teeth. For the genera Lasius, Temnothorax and Leptothorax this is particularly important.
  • For identification of Camponotus species, major workers are required (Hansen and Klotz 2005); however it is important to collect all castes, especially when dealing with arboreal species such as Camponotus nearcticus,whose majors can easily be confused with minors from larger Camponotus species.
  • For identification of Formica fusca group specimens there is a couplet in the key where some dissection is needed. This dissection is best done before the specimen is pointed. Remove the posterior four legs including the coxae, and then mount the specimen on its side; this will allow for structures required for identification to be seen.
  • For identification of Lasius, workers of several species are very similar (especially in the subgenus Acanthomyops). Characters of many of these species are most evident and less variable in the larger workers (Wilson 1955; Mackay and Mackay 2002), especially for mandibular tooth characters; therefore smaller specimens of a species can easily be confused.  To alleviate any confusion it is best to examine multiple specimens from a colony.
  • For identification of Myrmica species, when using antennal characters it is best to orient the antenna as pictured in Figs. 14a and 14b.  The base of the scape should be oriented perpendicular to the head so as to reveal laminal characters in posterior and anterior views.