Simplified key for identification American genera of Rhopalinae (Insecta, Heteroptera, Rhopalidae) with list of species
Simplified key for identification American genera of Rhopalinae (Insecta, Heteroptera, Rhopalidae) with list of species
Rhopalidae (or "scentless bugs"*) is a small (slightly more than 200 species), but widespread, common, and rather difficult to identify family. They are distinguished from other Coreoidea by absence of visible orifices of scent glands on thorax (or poorly visible). Here is a simplified key for identifying genera of the subfamily Rhopalinae recorded from the New World (with a list of American species). The most easily noticeable characters, usually clearly visible in photographs, are selected. For this reason, the key is not divided into tribes, as this division is based on characters that often require examination of the collection specimen with a microscope. A general distribution is given for the species listed: N - North America (north of Mexico), C - Central America (Mexico to Panama), S - South America (south of Panama). I am sincerely thankful to the iNaturalist users who posted their photos to which I refer.
* "The commonly applied name for this family, “scentless plant bugs,” reflects the absence of metathoracic scent glands in serinethines. However, this name is misleading and inappropriate because these and other rhopalids commonly produce redolent compounds from scent glands. Members of the more diverse subfamily, Rhopalinae, in fact possess fully functional metathoracic scent glands as adults, in common with other hemipterans. Moreover, both subfamilies retain the anterior dorsal abdominal gland usually found only in immature Heteroptera, and adult males also secrete fragrances from glands in the genitalia. " (Fowles et al., 2015 https://doi.org/10.1007/978-94-017-9861-7_20).
References:
family Rhopalidae Amyot & Serville, 1843: Coreoidea Species File. http://coreoidea.speciesfile.org/Common/basic/Taxa.aspx?TaxonNameID=1191054
True Bugs (Heteroptera) of the Neotropics (chapter: Scentless Plant Bugs (Rhopalidae)): https://doi.org/10.1007/978-94-017-9861-7_20
Catalog of the Heteroptera or True Bugs, of Canada and the Continental United States. https://doi.org/10.1201/9781351070447
Contribution to the knowledge of Patagonia, Argentina: redescription of the genus Xenogenus Berg 1883 (Hemiptera: Heteroptera: Rhopalidae) and description of immature stages of Xenogenus gracilis Reed, 1899. https://doi.org/10.11646/zootaxa.3919.3.7
Revision der Gattung Harmostes Burm., 1835. https://doi.org/10.1002/mmnz.19780540205
Revision der Gattung Stictopleurus Stål, 1872 (Heteroptera, Rhopalidae). https://www.zobodat.at/publikation_articles.php?id=339729
Revision der Gattung Liorhyssus Stål, 1870. (Heteroptera, Rhopalidae). https://doi.org/10.1002/mmnd.19760230117
A Revision of the Genus Arhyssus Stål. https://doi.org/10.1093/aesa/61.3.629
Revision of the New World Scentless Plant Bug Genus Niesthrea (Hemiptera: Heteroptera: Rhopalidae), with Descriptions of Six New Species and a Key to the Species. https://doi.org/10.1093/isd/ixz014
Family Rhopalidae
Subfamilies:
1- Pronotum with wide anterior collar, separated from the anterolateral margin by the incision. – Subfamily Serinethinae (American genera: Jadera and Boisea).
- Pronotum without the visible "collar", or at most with narrow smooth ring on the anterior margin of pronotum, separated by a deep furrow. – Subfamily Rhopalinae.
Subfamily Rhopalinae
(1a) Posterior femora large, noticeable thicker and longer than the median or anterior ones, with spines or teeth on apical (thickened) part of its ventral surface – 2
(1b) Posterior femora are the same as the mid ones, without ventral spines or teeth – 4
(2a) 4th (apical) antennal segment is longer than head. Anterolateral corner of pronotum isn’t produced forward as an acute tooth. Slender, similar to Alydinae in the appearance (https://www.inaturalist.org/photos/350613574). – Tribe Chorosomatini, genus Xenogenus Berg, 1883. Species (all American):
Xenogenus gracilis (Reed, 1899) – S.
Xenogenus picturatum Berg, 1883 – N (Arizona), C, S.
(2b) 4th (apical) antennal segment much shorter than head. Anterolateral corner of pronotum noticeable produced forward as an acute tooth. Wider, isn’t similar to Alydinae. – 3
(3a) Abdomen much wider than elytra, connexiva (its separated lateral part) visible well from above (https://www.inaturalist.org/photos/268645932). – Tribe Harmostini, genus Aufeius Stål, 1870. Monotypic, the only American species:
Aufeius impressicollis Stål, 1870 – N (more common in Southwest), C.
(3b) Abdomen not wider than elytra, connexiva (its separated lateral part) not visible or barely visible from above (with normal position of elytra) (https://www.inaturalist.org/photos/348085467). – Tribe Harmostini, genus Harmostes Burmeister, 1835. Species (all American):
Subgenus Harmostes Burmeister, 1835
Harmostes angustatus Van Duzee, 1918 – N, C.
Harmostes bilobatus Melo & Montemayor, 2011 – S.
Harmostes brevispinus Blöte, 1934 – S.
Harmostes disjunctus Barber, 1925 – S.
Harmostes dorsalis Burmeister, 1835 – N, C, S.
Harmostes enatus Brailovsky & Soria, 1981 – C.
Harmostes formosus Distant, 1881 – ? N (Texas), C.
Harmostes fraterculus (Say, 1832) – N, ? C.
Harmostes fusiformis Harris, 1942 – S.
Harmostes gravidator (Fabricius, 1794) – C, S.
Harmostes incisuratus Distant, 1881 – S.
Harmostes nebulosus Stål, 1862 – C.
Harmostes parafraterculus Göllner-Scheiding, 1978 – S.
Harmostes paraprolixus Göllner-Scheiding, 1998 – S.
Harmostes prolixus Stål, 1860 – S.
Harmostes reflexulus (Say, 1832) – N, C.
Harmostes rubrum Melo & Montemayor, 2011 – S.
Harmostes serratus Fabricius, 1775 – N (SE), C, S.
Harmostes signoreti Reed, 1899 – S.
Harmostes splendens Harris, 1944 – S.
Subgenus Neoharmostes Göllner-Scheiding, 1978
Harmostes apicatus Stål, 1859 – ? C, S.
Harmostes bergi Göllner-Scheiding, 1998 – S.
Harmostes confinis Harris, 1942
Harmostes corazonus Distant, 1893 – S.
Harmostes corizoides Jensen-Haarup, 1924 – S.
Harmostes imitabilis Harris, 1942 – S.
Harmostes insitivus Harris, 1942 – S.
Harmostes marmoratus (Blanchard, 1852) – S.
Harmostes minor (Spinola, 1852) – S.
Harmostes petulans Harris, 1942 – S.
Harmostes procerus Berg, 1878 – S.
I.s.
Harmostes montanus Grillo & Alayo, 1978 – C (Cuba).
(4a) Head is extremely wide: about twice as long and almost equal in with to posterior margin of pronotum (much wider than the anterior) (https://www.inaturalist.org/photos/302234776). Tribe Rhopalini, genus Brachycarenus Fieber, 1860. One introduced species in New World:
Brachycarenus tigrinus (Schilling, 1829) N, C (Old World native).
(4b) If head wider than long, it’s much narrower than posterior margin of pronotum (about equal to the anterior). – 5.
(5a) Metapleura not divided, its apical part has about the same punctation (https://www.inaturalist.org/photos/120844736), doesn't protrude sideways and is not clearly visible from above (https://www.inaturalist.org/photos/120844705). The transverse furrow in the anterior part of the pronotum laterally forms a closed or nearly closed loop (https://www.inaturalist.org/photos/120844513). Tribe Rhopalini, genus Stictopleurus Stål, 1872. American species:
Stictopleurus knighti Harris, 1942 – N.
Stictopleurus intermedius (Baker, 1908) – N.
Stictopleurus plutonius Baker, 1908 – N.
Stictopleurus punctiventris (Dallas, 1852) – N, C.
Stictopleurus viridicatus (Uhler, 1872) – N, C (NW Mexico).
(5b) Metapleura divided in two different parts, apical one has much sparser and smaller punctation (https://www.inaturalist.org/photos/120843406), protrude sideways and is clearly visible from above (https://www.inaturalist.org/photos/120843377). The transverse furrow in the anterior part of the pronotum laterally simple, without the loop – 6.
(6a) Pronotum have a "collar" – narrow smooth ring on the anterior margin of pronotum, separated by a deep furrow (https://www.inaturalist.org/photos/120844269). Length of the 4th (apical) antennomere is much more than interocular distance and almost equal to the width of the head with eyes. Tribe Rhopalini, genus Liorhyssus Stål, 1870. Species recorded from New World:
Liorhyssus hyalinus (Fabricius, 1794) – N, C, ? S (introduced from Old World).
Liorhyssus kaltenbachi Göllner-Scheiding, 1976 – S.
Liorhyssus lineatoventris (Spinola, 1852) – S.
(6b) Pronotum without such a "collar" (https://www.inaturalist.org/photos/120843655). Length of the 4th (apical) antennomere is little more than interocular distance and much less than the width of the head with eyes. – 7.
(7a) Head much wider than long. Labium extends from the posterior margin of the hind coxae to abdominal segment IV. Tribe Niesthreini, genus Arhyssus Stål, 1870. Species (all American):
Arhyssus barberi Harris, 1942 – N.
Arhyssus confusus Chopra, 1968 – N.
Arhyssus crassus Harris, 1942 – N.
Arhyssus distinctus Chopra, 1968 – N.
Arhyssus hirtus Torre-Bueno, 1912 – N.
Arhyssus lateralis (Say, 1825) – N, C.
Arhyssus longirostratus Chopra, 1968 – N.
Arhyssus nigristernum (Signoret, 1859) – N.
Arhyssus parvicornis (Signoret, 1859) – N, C.
Arhyssus peruensis Chopra, 1968 – S.
Arhyssus pilosus (Signoret, 1859) – S.
Arhyssus punctatus (Signoret, 1859) – N, C.
Arhyssus rubrovenosus Scudder, 2008 – N.
Arhyssus schaeferi Chopra, 1968 – N.
Arhyssus scutatus (Stål, 1859) – N.
Arhyssus slateri Chopra, 1968 – C.
Arhyssus tricostatus (Spinola, 1852) – S.
Arhyssus usingeri Harris, 1942 – N.
Arhyssus validus (Uhler, 1893) – N, C.
(7b) Head is of about equal length and width. Labium isn’t extending beyond the hind coxae. Tribe Niesthreini, genus Niesthrea Spinola, 1837. Species (all American):
Niesthrea agnes Chopra, 1973 – S.
Niesthrea brevicauda Chopra, 1973 – S.
Niesthrea casinii Göllner-Scheiding, 1984 – S.
Niesthrea choprai Melo & Henry, 2019 – S.
Niesthrea conicoloba Melo & Henry, 2019 – S.
Niesthrea dentata Chopra, 1973 – S.
Niesthrea digna Chopra, 1973 – S.
Niesthrea fenestrata (Signoret, 1859) – S.
Niesthrea flava Grillo & Alayo, 1978 – S.
Niesthrea josei Göllner-Scheiding, 1989
Niesthrea lateroloba Melo & Henry, 2019 – S.
Niesthrea louisianica Sailer, 1961 – N, C.
Niesthrea parvaloba Melo & Henry, 2019 – S.
Niesthrea pictipes (Stål, 1859) – C, S.
Niesthrea rostrata Melo & Henry, 2019 – S.
Niesthrea sidae (Fabricius, 1794) – N, C.
Niesthrea similis Chopra, 1973 – C, S.
Niesthrea truncata Melo & Henry, 2019 – S.
Niesthrea ventralis (Signoret, 1859) – C, S.
Niesthrea vincentii (Westwood, 1842) – S.
