Geraeus Pascoe, 1889

Prena, Jens, 2009, A Review of the Species of Geraeus Pascoe and Linogeraeus Casey Found in the Continental United States (Coleoptera: Curculionidae: Baridinae), The Coleopterists Bulletin 63 (2), pp. 123-172 : 130-140

Geraeus Pascoe

Curculio of authors (not Linnaeus 1758).

Balaninus of authors (not Germar 1817).

Baridius of authors (not Schönherr 1825).

Centrinus of authors (not Schönherr 1825).

Toxeres Germar 1829:359 . Type species, Balaninus pistor Germar 1824 , by original designation. Synonymized with Centrinus Schönherr by Alonso- Zarazaga and Lyal (1999). New synonym, nomen oblitum.

Toxeres Schönherr 1833:22 (not Germar 1829). Type species, Balaninus pistor Germar 1824 , by original designation.

Toxerus of authors (misspelling of Toxeres ).

Geraeus 1889:323 Pascoe. Type species, Centrinus senilis Gyllenhal 1836 , by monotypy. Nomen protectum.

Centrinus , subgenus Geraeus . Casey (1920).

Centrinaspis Casey 1920:391 . Type species, Centrinus perscillus Gyllenhal 1836 (5 Curculio picumnus Herbst 1797 ), by original designation. Synonymy with Geraeus by Kuschel (1983).

Pycnogeraeus Casey 1920:389 . Type species, Centrinus modestus Boheman 1836 , by original designation. New synonymy.

Diversity. Approximately 160 species are presently assigned to Geraeus . Ten species occur in the continental United States.

Distribution. Species of Geraeus occur in the temperate and tropical zones of the Americas including the West Indies.

Larval hosts. Asteraceae : Helenium amarum Raf. (5 tenuifolium Nutt.) (R. Cushman, observation), Montanoa sp. (K. Nishida, rearing record). Commelinaceae : Commelina sp. (P. Sullivan, C. W. O’Brien, J. Prena, observations), Tradescantia sp. (E. Riley, observation). Poaceae : Panicum dichotomiflorum Michx. (G. Ainslie, observation), Zea mays L. (Ainslie 1920; Kirk 1965).

Biology. Life history data of Geraeus species are scarce and generalizations cannot be made at this point. The larva of G. penicillus frequently bores in the stalk of Z. mays (Ainslie 1920; Kirk 1965) and is said to overwinter in the soil (Ainslie 1920). However, adult specimens emerged from P. dichotomiflorum in Texas in early November, and another specimen is labeled as being bred from a flower head of H. amarum (all specimens in USNM). Ainslie (1920) ascribed the infestation of the stems of Echinochloa crusgalli (L.) Beauv. and P. dichotomiflorum to G. penicillus . I was unable to distinguish these larvae and others obtained from rice and unidentified grasses (all at USNM) from larvae of G. penicillus that were verified by rearing. Several observations suggest that G. senilis is another species associated with Z. mays . The larva of an undescribed Costa Rican species develops in Montanoa sp. and pupates in the stem (K. Nishida, pers. comm.). Geraeus coarctatus and G. modestus seem to be associated with Commelinaceae , while the closely related G. patagoniensis is not. The number of instars is not known for any species of Geraeus .

Economic importance. Geraeus penicillus , apparently the only species with a completely explored life cycle, is frequently associated with Z. mays . Ainslie (1920) reported variable degrees of infestation in Tennessee, up to 100%. Kirk (1965) noted that although the presence of the larva had been known for a long time in the southern United States, its impact on crop and plant health apparently has never been investigated. His own survey showed an average 70–80% infestation of corn stalks, with an estimate of over 8,000 larvae per acre [ca. 2 m 22]. Young plants of Z. mays were attacked by numerous Geraeus species at the Escuela Agrícola Panamericana, Honduras (R. Cave, pers. comm.). Fernández (1998) observed G. penicillus in association with sugarcane in Cuba. Because the development of Geraeus species often seems to be completed in the soil and the impact caused by the larva usually is not linked to the weevil, there seems to be little awareness of the potential implications in agriculture.

Nomenclature. Pascoe (1889) proposed Geraeus and thirteen other genera for species he considered improperly placed in Centrinus Schönherr. Although this

0.5 mm. 57) G. minor ; 58) G. coarctatus ; 59) G. pannuceus ; 60) L. appalachensis .

action was nomenclaturally valid and well-founded, the proposal was made in a rather informal fashion; Pascoe never used those genera himself except in the key. Casey (1892) was the first to adopt Geraeus Pascoe , at the subgeneric level as a proxy for his Centrinus subgenus IV. Champion (1908) discussed the difference between Geraeus and Centrinus and placed a total of 108 species in Geraeus (Champion 1908, 1909, 1910). This diversity plus the usage of the word in composite generic names by Champion (1908), Casey (1920, 1922), and Bondar (1942) led to a general familiarity of entomologists with the name Geraeus . However, all authors overlooked or ignored Toxeres Germar (1829) and Toxeres Schönherr (1833) , with the type species Balaninus pistor Germar. Toxeres was not listed in Gemminger and Harold (1871), Leng (1920), Hustache (1938), Blackwelder (1947), O’Brien and Wibmer (1982), and Wibmer and O’Brien (1986). Zarazaga and Lyal (1999) maintained Toxeres as invalid by provisionally[?] placing it in synonymy with Centrinus , even though the type species was described from Kentucky, where Centrinus does not occur. Anderson (2002) commented briefly on this issue but maintained the status quo because he had not seen the species. Balaninus pistor Germar is a subjective junior synonym of Curculio penicillus Herbst (new synonymy). Based on Kuschel’s (1983) concept of Geraeus , Toxeres Germar is a subjective senior synonym of Geraeus Pascoe (new

synonymy). ICZN Article 23.9.1 demands reversal of precedence given that (1) the senior name has not been used as valid after 1899, and (2) it can be demonstrated that the junior name has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years and encompassing a span of not less than 10 years. The following citations fulfill the second requirement: Arnett (1962:108.38), Kissinger (1964:84), Silva et al. (1968:469), O’Brien and Wibmer (1982:194, 1984:299), Kuschel (1983:37), Wibmer and O’Brien (1986:305, 1989:22), Anderson (1993: 221, 2002:746), Anderson and Peck (1994:827), Jiménez et al. (1994:235), Anderson and O’Brien (1996:337), Downie and Arnett (1996:1623), Peck and Thomas (1998:145), Alonso-Zarazaga and Lyal (1999:99), Emlen and Nijhout (2000:674), Bloem et al. (2002:635), Morrone et al. (2002:155), Matienzo et al. (2003:50), Lozada et al. (2004:106), Peck (2005:220), Salas and Boradonenko (2006:52), Ødegaard and Frame (2007:706), and Prena (2008:243). Because Toxeres Germar and its homonym and objective synonym, Toxeres Schönherr , have not been regarded as valid names after 1899, the first requirement is also fulfilled. Herewith I conserve Geraeus Pascoe as a nomen protectum and suppress its unused senior synonyms Toxeres Germar and Toxeres Schönherr as nomina oblita.

Discussion. Champion (1908) was the first to distinguish between species with a smooth versus a denticulate inner mandibular face and he applied the name Geraeus to the former. Casey (1920, 1922) restricted Geraeus to species with the inner mandibular face distally diverging and proposed numerous new genera for the others. Kuschel (1983) recognized as valid only Geraeus , Linogeraeus , and Leptocorynus Casey based on the folds, pits, and setal patterns of the prosternum and the shape of the antennal club, but his argumentation did not include all relevant genera, among them Pachygeraeus and Pycnogeraeus . The concept of Geraeus adopted here is that of Kuschel (1983) with the modifications outlined below.

Casey (1920) proposed Pycnogeraeus apparently based on characters he had presented earlier ( Casey 1892) for Centrinus subgenus I, i.e., well-developed prosternal spines in male, scape not reaching eye, anterior coxae narrowly separated, body robust, and rostrum thick. He divided his previously informal group into two new genera, Pachygeraeus and Pycnogeraeus , without directly comparing the diagnostic character states. Pycnogeraeus included three synonyms of a single species; a second [unrelated] species was suggested as possibly belonging here, but this transfer was not made due to lack of male specimens. The nebulous description was further confused two pages later where Casey (1920:391) included the closely related Geraeus basinotatus Champion in Centrinaspis Casey. Sleeper (1954) disregarded those genera when he described the closely related G. patagoniensis . None of these authors offered a comparison with other described species of this complex, such as G. amplicollis Champion , G. coarctatus Champion , and G. iners Champion. Kissinger (1964) tried to infer the concepts of Casey’s genera and incorporated in his generic key the presence and shape of the prosternal pit. However, he acknowledged that Casey assigned species rather inconsistently to Pachygeraeus , Pycnogeraeus , and Centrinaspis and questioned the distinctness of these genera. Kuschel (1983) disregarded as a valid character the apically divergent mandibles and proposed a new classification largely based on Neotropical material. Downie and Arnett (1996) and Anderson (2002) essentially followed Kissinger (1964) and maintained Pycnogeraeus as a distinct genus; Anderson did so with an attempt to implement Kuschel’s (1983) results. However, all aforementioned authors relied on the prosternal pit, seemingly unaware of its presence in numerous Geraeus and Linogeraeus species (e.g., Figs. 3, 5 ) and Kissinger’s (1964:80) footnote pointing out discrepancies between his and Casey’s classification. As neither of the previous authors nor I could recognize a meaningful concept for Pycnogeraeus in Casey’s description and actions, I propose here Pycnogeraeus Casey as a new synonym of Geraeus Pascoe. The hammer-shaped appendix of the male flagellum ( Figs. 58, 59 ) cannot be used to define a separate genus, as it occurs in G. coarctatus , G. modestus , G. pannuceus , and G. patagoniensis , is notably modified in G. basinotatus , and absent in some other undescribed species of this complex.

My own study showed that several species cannot be assigned unequivocally to Geraeus or Linogeraeus based on the morphology of the prosternum, and that this is particularly true for male specimens. A basal sclerite is present in the internal sac of the larger-sized Geraeus species inhabiting the United States, but in none of the three small-sized species, G. minor , G. petilior , and G. picumnus . While G. picumnus clearly concurs with Kuschel’s concept of Geraeus , G. minor and G. petilior would be examples of ambiguous placements. However, based on the presence of separate punctures on the tubular constriction of the prosternum and the rather linear arrangement of the scales, provisionally I assign these two doubtful cases to Geraeus .

Figures

Figs. 1–8. Geraeus and Linogeraeus species, anterior portion of prosternum. 1) G. modestus, male; 2) G. modestus, female; 3) G. picumnus, male; 4) G. picumnus, female; 5) L. finitimus, male; 6) L. finitimus, female; 7) L. laevirostris, male; 8) L. urbanus, male.

Figs. 57–60. Geraeus and Linogeraeus species, aedeagus, dorsal aspect; scale bars