Crematogaster (Orthocrema),

Ward, Philip S. & Blaimer, Bonnie B., 2022, Taxonomy in the phylogenomic era: species boundaries and phylogenetic relationships among North American ants of the Crematogaster scutellaris group (Formicidae: Hymenoptera), Zoological Journal of the Linnean Society 194, pp. 893-937 : 902-903

CREMATOGASTER (ORTHOCREMA)

C. corvina Mayr, 1870: 994

C. crinosa Mayr, 1862: 767 (for list of junior synonyms see Longino, 2003: 49)

C. minutissima Mayr, 1870: 995

C. missouriensis Emery, 1895: 287

= C. minutissima smithi Creighton, 1950: 205 (synonymy by Shattuck & Cover, 2016: 15)

C. obscurata Emery, 1895: 287 = C. agnita Wheeler, 1934b: 175 (synonymy by Longino, 2003: 97) C. torosa Mayr, 1870: 404 = C. arizonensis Wheeler, 1908: 482 (synonymy by Longino, 2003: 120) = C. brevispinosa tumulifera Forel, 1899: 84 (synonymy by Longino, 2003: 120)

From the preceding list, the Crematogaster fauna of the United States and Canada is seen to comprise 33 species: 27 species of Crematogaster (Crematogaster) , all members of the C. scutellaris group, and six species of Crematogaster (Orthocrema) . An additional species in the C. scutellaris group, of uncertain identity, occurs in southern Arizona. It is referred to as Crematogaster sp. cf. opaca in the key and in remarks below.

The following Crematogaster (Crematogaster) taxa are treated in individual species accounts after the key: Crematogaster browni , C. californica , C. cedrosensis , C. cerasi , C. colei , C. depilis , C. detecta , C. hespera , C. larreae , C. marioni , C. opaca , C. opuntiae , C. parapilosa , C. pilosa , C. punctulata , C. rossi , C. vermiculata and C. vetusta.

WORKER- BASED KEY TO SPECIES OF CREMATOGASTER IN AMERICA NORTH OF MEXICO

This key is broadly based on Buren (1968), but updated to incorporate recent discoveries and more quantitative measures of species differences. The user is cautioned that the species-level taxonomy of these ants has not been fully resolved, especially among the complex of species related to Crematogaster californica and C. depilis , and among taxa found in Mexico (the latter not treated here). In some couplets we have been forced to characterize species based on several features, no single one of which is diagnostic by itself. The second lug of such couplets is often of the form ‘without this combination of characters’, followed by a series of conditional statements. This makes the key somewhat cumbersome but we can find no other way to accurately account for the variation observed within and among species.

Features of pilosity assume importance in many couplets, and they will be difficult or impossible to assess accurately in specimens that are badly worn or covered in glue. Use of soft (fluorescent) light and an effective specimen manipulator that permits viewing from all angles and with varying degrees of backlighting will greatly assist in discerning differences in pilosity and sculpture. Accurate linear measurements are also critical for identification of many of these species. Differences among species are sometimes less pronounced in the smallest workers, so if the choice exists, it is advisable to use the larger workers of a series for identification.

To assist the user we provide images of some of the more salient morphological features that are cited in the key ( Figs 3–12 ), as well as standard views of the worker caste of each species in the C. scutellaris group ( Figs 13–39 ). However, images of single specimens do not provide information about the variability of each species. Linear measurements, ratios of measurements and setal counts more accurately capture such variation. Bivariate plots of these measurements can sometimes be helpful for distinguishing species ( Figs 40–47 ).

Figures

Figures 3–12. Crematogaster worker features useful for identification. 3, petiole shape, dorsal view, C. lineolata (CASENT0863235) (3A) and C. torosa (CASENT0795540) (3B); 4, sculpture on declivitous face of propodeum, C. dentinodis (CASENT0863070) (4A) and C. depilis (CASENT0863478) (4B); 5, mesosomal pilosity, C. punctulata (CASENT0863277) (5A) and C.emeryana (CASENT0863099) (5B); 6, position and shape of propodeal spines, dorsal view, C.isolata (CASENT0863072) (6A) and C.pinicola (CASENT0882129) (6B); 7, petiole shape, dorsal view, C.mutans (CASENT0862488); 8, subpetiolar tooth, lateral view, C.mutans (CASENT0862488); 9, promesonotal sculpture, C.californica (CASENT0221085)(9A) and C.coarctata (CASENT0221962) (9B); 10, postpetiolar seta, C. browni (CASENT0863144) (10A) and C. cerasi (CASENT0795541) (10B); 11, cephalic pilosity, C. torosa (CASENT0795540) (11A) and C. missouriensis (CASENT0221041) (11B); 12, mesosomal profile, C. crinosa (CASENT0795543) (12A) and C. torosa (CASENT0863226) (12B).

Figures13–18. Crematogaster workers,showing lateral viewof body (A),full-faceview of head(B) and dorsalview ofbody (C). 13, C. dentinodis (CASENT0102830); 14. C. vetusta holotype (CASENT0863254); 15, C. navajoa worker (CASENT0064826); 16, C. punctulata lectotype (CASENT0923318); 17, C. isolata (CASENT0922731); 18, C. sp. cf. opaca (MCZENT00589113). Images courtesy of AntWeb (www.antweb.org); photographers Jen Fogarty (13), Michele Esposito (14, 16), April Nobile (15), Wade Lee (17), Zachary Griebenow (18).

Figures 19–24. Crematogaster workers, showing lateral view of body (A), full-face view of head (B) and dorsal view of body (C). 19, C. mutans worker (CASENT0922736); 20, C. colei (CASENT0922726); 21, C. detecta holotype (CASENT0863461); 22, C. larreae paratype (CASENT0005943); 23, C. depilis (CASENT0005668); 24, C. californica lectotype (CASENT0923319). Images courtesy of AntWeb (www.antweb.org); photographers Wade Lee (19, 20), Zachary Griebenow (21), April Nobile (22, 23), Michele Esposito (24).

Figures 25–30. Crematogaster workers, showing lateral view of body (A), full-face view of head (B) and dorsal view of body (C). 25, C. opuntiae (CASENT0922738); 26, C. marioni (CASENT0922734); 27, C. coarctata (CASENT0005667); 28, C. hespera holotype (USNMENT00529501); 29, C. browni (CASENT0922722); 30, C. emeryana (CASENT0922729). Images courtesy of AntWeb (www.antweb.org); photographers Wade Lee (25, 26, 29, 30), April Nobile (27), Michele Esposito (28).

Figures 31–36. Crematogaster workers, showing lateral view of body (A), full-face view of head (B) and dorsal view of body (C). 31, C. cerasi lectotype (USNMENT00529078); 32, C. vermiculata (CASENT0914534); 33, C. rifelna holotype (LACMENT164556);34, C.ashmeadi (CASENT0922720); 35, C.pinicola (CASENT0172943); 36,C.pilosa(CASENT0914530). Images courtesy of AntWeb (www.antweb.org); photographers Michele Esposito (31, 33), Zach (Ziv) Lieberman (32, 36), Wade Lee (34), April Nobile (35).

Figures 37–39. Crematogaster workers, showing lateral view of body (A), full-face view of head (B), and dorsal view of body (C). 37, C.parapilosa holotype (CASENT0863386); 38, C. laeviuscula (CASENT0104828); 39, C.lineolata (CASENT0922733). Images courtesy of AntWeb (www.antweb.org); photographers Zachary Griebenow (37), April Nobile (338), Wade Lee (39).

Figures 40–47. Bivariate plots of selected worker measurements in the Crematogaster scutellaris group. 40, PP-SL (postpetiole seta length) by HW (head width) in C. browni (N = 16) and C. cerasi (N = 17); 41, ED (eye diameter) by MtFL (metafemur length) in C. californica (N = 22) and C. coarctata (N = 21); 42, MtFL (metafemur length) by HW (head width) in C. californica (N = 22), C. colei (N = 12) and C. opuntiae (N = 10); 43, MtFL (metafemur length) by HW (head width) in C. depilis (N = 15), C. detecta (N = 11) and C. larreae (N = 5); 44, MtTL (metatibia length) by HW (head width) in C. depilis (N = 15), C. detecta (N = 11) and C. larreae (N = 5); 45, SPL (propodeal spine length) by HW (head width) in workers of C. hespera (N = 18), C. laeviuscula (N = 25) and C. parapilosa (N = 15); 46, SL (scape length) by HW (head width) in C. emeryana (N = 12) and C. marioni (N = 18); 47, SPTD (propodeal spine tip distance) by HW (head width) in C. lineolata (N = 26) and C. punctulata (N = 15).