Linogeraeus Casey

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 : 152-155

Linogeraeus Casey

Curculio of authors (not Linnaeus 1758).

Centrinus of authors (not Schönherr 1825).

Geraeus of authors (not Pascoe 1889).

Linogeraeus Casey 1920:390 . Type species, Centrinus lineellus LeConte , by original designation.

Conocentrinus Casey 1920:409 . Type species, Conocentrinus tenuirostris Casey , by original designation. Synonymy by Kuschel (1983:38).

Glyptogeraeus Casey 1920:458 . Type species, Centrinus punctatissimus Boheman , by original designation. Synonymy by Kuschel (1983:38).

Pachygeraeus Casey 1920:388 . Type species, Centrinus laevirostris LeConte , by original designation. New synonymy.

Brachygeraeus Casey 1922:228 . Type species, Brachygeraeus bellulus Casey , by original designation. Synonymy by Kuschel (1983:38).

Centrinaspidia Casey 1922:230 . Type species, Centrinaspidia mundula Casey , by original designation. Synonymy by Kuschel (1983:38).

Centrinaspis ; Casey (1922:110), see discussion below.

Lepidobaris Lea 1927:370 (not Champion 1909). Type species, Lepidobaris metasternalis Lea (5 Centrinus urbanus Boheman ), by original designation. Synonymy by Kuschel (1983:38).

Geraeus , subgenus Linogeraeus . Hustache (1938:96).

Diversity. Approximately 75 species are presently assigned to Linogeraeus . Possibly nine native and at least two adventive species occur in the continental United States.

Distribution. Species of Linogeraeus occur in the temperate and tropical zones of the Americas including the West Indies. Linogeraeus urbanus (Boheman) is established in Australia and New Zealand; L. punctatissimus (Boheman) has been found in La Coruña, Spain 1929 (USNM).

Larval host. Poaceae : Agrostis stolonifera L. [5 Agrostis alba L.)] (Luckmann and LeSar 1959), Paspalum distichum L. [5 Paspalum paspaloides (Michx.) Scribn. )] (May 1984), Z. mays (label data).

Biology. There are considerable inconsistencies in what is known about Linogeraeus species. May (1984) recognized five larval instars in L. urbanus , with a prepupal stage apparently overwintering in the plant before pupation takes place in the soil. The adult weevil did not survive the winter [in New Zealand]. Luckmann and LeSar (1959) recognized three larval instars in L. capillatus , no prepupal stage, and after pupation in the soil, the adult weevil overwintered [in the United States]. However, they noticed a relocation of the last instar larva in the soil, after 30–40 days of relative inactivity, before pupation; this could indicate development of a prepupa. These two weevil species showed a high degree of hostspecificity. A series of L. tonsilis was reared in New Mexico from stalks of Z. mays (Harrison and Fraser, label data) but no details are known. One specimen is teneral and deformed, and it appears as if the series was taken directly from the plant and pupation did not take place in the soil.

Economic importance. Luckmann and LeSar (1959) investigated L. capillatus in southern Illinois and estimated up to 75% reduced seed production in redtop, A. stolonifera . May (1984) studied the life history of L. urbanus in New Zealand, where it was introduced accidentally and occurred in association with the equally introduced mercer grass, P. distichum . She concluded that weevil and grass were of little economic importance. Adverse effects on Z. mays have not been documented for L. tonsilis . However, the impact of Linogeraeus species on agriculturally used grasses may not be fully understood because the weevils’ metamorphosis often is completed outside the host.

Discussion. Casey (1920:390) proposed Linogeraeus for his provisional Centrinus subgenus VII ( Casey 1892:576). The chief distinguishing character seems to have been the elytral color pattern. Two years later, Casey (1922:110) invalidated Linogeraeus by considering it a synonym of Centrinaspis Casey , now emphasizing the shapes of the mandibles and the second desmomere. This action was overlooked by Hustache (1938), Blackwelder (1947), and O’Brien and Wibmer (1982), who considered Linogeraeus a subgenus of Geraeus while maintaining Centrinaspis as a separate genus. Kuschel (1983) pointed out the absence of longitudinal folds on the prosternum and the peculiar arrangement of the scales, which radiate from a central point of the prosternum rather than being orientated distad ( Fig. 6 ), a condition also noticed by Faust (1896:117). Kuschel proposed a simplification of the confusing generic classification of these weevils and recognized three genera, Geraeus , Linogeraeus , and Leptocorynus , apparently also overlooking the synonymy of Linogeraeus and Centrinaspis . However, this is without nomenclatural relevance, because Casey’s (1922) synonymy does not affect the availability of Linogeraeus as the senior name for a genus distinct from Centrinaspis . The prosternal pore, from where scales radiate, probably is derived from two amalgamated median punctures, which usually are well-preserved in Geraeus species.

Anderson (2002:743) distinguished Pycnogeraeus and Pachygeraeus from Geraeus and Linogeraeus based on the prosternal excavation in the male (couplet 42) as suggested by Kissinger (1968). However, this character is also developed in numerous Geraeus and Linogeraeus species (e.g., Figs. 3, 5 ). Kuschel’s (1983) classification based on prosternal morphology would group Pycnogeraeus with Geraeus , and Pachygeraeus with Linogeraeus . This arrangement is generally supported by morphological details of the male genitalia, in particular the sclerite of the internal sac, although deviations occur in small-sized Geraeus species. Linogeraeus appalachensis is morphologically intermediate to the type species of Pachygeraeus , P. laevirostris (LeConte) , and partially resembles the somewhat deviating elliptical shape of that species. The three species currently placed in Pachygeraeus are synonyms and show no apparent synapomorphy. Although a comprehensive study of all included species may give reasons to further modify Linogeraeus sensu Kuschel , it is more advantageous at this stage to maintain them in one genus under consistent criteria. Pachygeraeus Casey is proposed here as a

new synonym and included in Linogeraeus Casey.

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.