Canadian Journal of Arthropod Identification

Taxonomic revision of the Nearctic erosa species group of Phymata Latreille, 1802 (Heteroptera: Reduviidae: Phymatinae)

CJAI 41 -- October 1, 2020

Paul Masonick & Christiane Weirauch

| Abstract | Introduction | Checklist | Materials & Methods | Species Key | Taxonomy | Acknowledgments | References | PDF | Cite |
| Appendix |


The genus Phymata Latreille, 1802 (Heteroptera: Reduviidae) comprises ~110 species of ambush bugs distributed primarily in the New World (Froeschner and Kormilev 1989). Their peculiar morphology, sexual dimorphism, and predation on other flower-associated arthropods have made them popular subjects for evolutionary (Punzalan et al. 2008a; Punzalan et al. 2008b, c, 2010, Weirauch et al. 2011; Punzalan and Rowe 2015, 2016), ecological (Balduf 1941; Mason 1977, 1986; Yong 2005; Masonick et al. 2019), and behavioral research (Dodson and Marshall 1984; Elliott and Elliott 1991, 1994; Yong 2003; Dixon and Rasmussen 2013). While these sit-and-wait predators are easily distinguished from other true bugs by their raptorial forelegs, fusiform antennae, deep antennal excavations of the head and propleura, and dorsolaterally flared pronotum and abdomen, species-level identification within the genus is confounded by subtle interspecific differences, sexual dimorphism, and intraspecific variation. This paradox holds especially true for the Nearctic erosa species group, a clade represented by the predominant ambush bug fauna of North America. While the vast majority of Phymata found in the wild and in collections belong to just a few common and widespread erosa group species, many rare endemic species are found in the deserts and scrublands of the western United States and northern Mexico.

The Nearctic erosa group, and Phymata as whole, have a convoluted taxonomic history. Taxonomic research on ambush bugs began when Linnaeus in 1758 described the first species, Cimex erosus, based on a specimen from Surinam. Latreille erected the genus Phymata in 1802 and reclassified C. erosus as Phymata erosa in 1804, a name under which numerous Neotropical and Nearctic subspecies would later be classified. Handlirsch (1897) provided the first monograph to focus exclusively on Phymatinae, and subsequent revisions by Melin (1931), Evans (1931), and Kormilev (1962) further refined understanding of their diversity, and over time, all Nearctic P. erosa subspecies were elevated to species rank. In addition to biological issues such as polymorphic traits and sexual dimorphism that hinder species diagnosis, the taxonomy of the erosa group has been complicated by the loss or lack of designated types, vague and/or poorly illustrated descriptions, and descriptions based on singleton specimens or on only one sex. What is more, coloration, a feature that can be quite variable within populations and one that changes drastically over time both in live and pinned specimens (Schuh and Slater 1995; Boyle and Start 2020), was used in many cases to define taxa. Outdated descriptions and keys, the most recent having been published in 1962, have culminated in numerous specimens in natural history collections being mis- or unidentified. While little has been done to modernize ambush bug taxonomy, molecular phylogenetics and integrative species delimitation have recently shed light on their species-level relationships and revealed that several erosa group taxa are para- or polyphyletic (Masonick et al. 2017; Masonick and Weirauch 2020). Taxonomic updates are sorely needed and insights from these analyses have helped structure the present revision.

The primary aim of this revision is to alleviate confusion pertaining to erosa group taxa by providing illustrated keys and detailed species diagnoses. To circumvent the issue of subtle or polymorphic characters and increase the chances of correct identification, our diagnoses reference suites of traits relevant for identifying each taxon, and do not rely on any single attribute. Prior to this project, 11 erosa group species and 11 subspecies were known from the Nearctic (Kormilev 1962; Froeschner and Kormilev 1989). Herein, we recognize 17 Nearctic erosa species partly through the synonymization or elevation of subspecies to full species of the taxa cataloged by Froeschner and Kormilev. Eleven previously accepted species are redescribed, five subspecies are elevated to species rank and redescribed, and one new species from southern California is described: Phymata paraborica sp. nov. Phymata americana coloradensis Melin, 1931 syn. nov., Phymata pacifica hainesi Kormilev, 1962 syn. nov., Phymata granulosa chiriquiensis Melin, 1931 syn. nov., and Phymata granulosa evansi Kormilev, 1962 syn. nov. are each synonymized with their respective nominate subspecies. Phymata fasciata panamensis Kormilev, 1962 syn. nov. is synonymized with Phymata mexicana Melin, 1931. Phymata granulosa texasana Kormilev, 1957 syn. nov. is synonymized with Phymata rossi Evans, 1931.

Provided in this revision are two illustrated keys to Nearctic ambush bugs. The first (Key(1)), covers rare non-erosa group Phymata native to the United States and Canada. The second (Key(2)) deals exclusively with the 17 species of the Nearctic erosa group clade. Detailed diagnoses, habitus plates, and distribution maps for these taxa are also included. Our treatment of the Nearctic erosa group benefited from the examination of more than 4,125 specimens from 14 natural history collections and survey of 2,290 (as of October 2019) transcontinental citizen science observations from our iNaturalist project “Uncovering the ambush bugs” (

For a list of all Phymata known from Canada, the United States, and/or Mexico, see Table 1. Ambush bugs native to North America that are not part of the erosa group clade are excluded from this revision. It should be noted that Phymata severini Handlirsch, 1897 and Phymata parva Handlirsch, 1897 are two taxa from Mexico that were originally erected as subspecies of P. erosa and later elevated to species rank by Melin (1931) and Kormilev (1962), respectively. Based on molecular analysis, we found these two species to both be distantly related to the clade of Nearctic ambush bugs treated here (see Masonick and Weirauch, 2020, Figs S3–S6).

Table 1. Checklist of Phymata found in Canada, the United States, and/or Mexico.

Phymata Latreille, 1802 (Heteroptera: Reduviidae)
    Phymata albopicta Handlirsch, 1897 (USA, MEX)
    Phymata annulipes Stål, 1862 (MEX)
    Phymata barberi Kormilev, 1962 (MEX)
    Phymata brailovskyi Kormilev, 1990 (MEX)
    Phymata luxa Evans, 1931 (USA, MEX)
    Phymata maculata Kormilev, 1957 (USA)
    Phymata noualhieri Handlirsch, 1897 (USA, MEX)
    Phymata pallida Kormilev, 1957 (USA)
    Phymata parva Handlirsch, 1897 (MEX)
    Phymata rhynocerata Kormilev, 1957 (MEX)
    Phymata severini Handlirsch, 1897 (MEX)
    Phymata turnbowi Kormilev, 1983 (MEX)
    Phymata vicina Handlirsch, 1897 (CAN, USA)

    erosa species group clade
        Phymata americana Melin, 1931 (CAN, USA, MEX)
        Phymata arctostaphylae Van Duzee, 1914 (USA, MEX)
        Phymata borica Evans, 1931 (USA)
        Phymata fasciata (Gray, 1832) (USA, MEX)
        Phymata granulosa Handlirsch, 1897 (MEX)
        Phymata luteomarginata Kormilev, 1957 (USA)
        Phymata metcalfi Evans, 1931 stat. restit. (CAN, USA)
        Phymata mexicana Melin, 1931 stat. nov. (MEX)
        Phymata mystica Evans, 1931 stat. restit. (USA)
        Phymata obscura Kormilev, 1957 stat. nov. (USA)
        Phymata pacifica Evans, 1931 (USA, MEX)
        Phymata paraborica sp. nov. (USA)
        Phymata pennsylvanica Handlirsch, 1897 (CAN, USA)
        Phymata rossi Evans, 1931 (USA)
        Phymata saileri Kormilev, 1957 (USA)
        Phymata salicis Cockerell, 1900 (USA)
        Phymata stanfordi Evans, 1931 stat. nov. (USA)