Neogerris lotus (White, 1879)

(Figs. 4, 5D–L, 6A)

Limnogonus lotus White, 1879a: 488 (original description).

Limnogonus celeris Drake & Harris, 1934: 214 (original description) (new synonym).

Neogerris celeris: Andersen 1975: 22–23 ( Gerrinae generic reclassification, changed combination).

Neogerris lotus: Andersen 1975: 22–23 ( Gerrinae generic reclassification, changed combination).

Identification. This species is very similar to N. lubricus, with about the same body length, but the pronotum posterior lobe usually reaches to only half of the mesonotum (Fig. 4E). However, the apterous specimens from Rio Grande do Norte have the pronotum completely covering the mesonotum (Figs. 5D, H), which is a rarer condition (see Nieser 1994). We identified our specimens as N. lotus based on male abdominal tergum VIII broad with the lateral margins parallel, and bearing a notch on its posterior margin (Figs. 4F–G, 5J–L), which is absent in N. lubricus (Fig. 5A)—although in some specimens the notch is not as prominent as in the illustration given by Drake & Harris (1934).

Lectotype designation. Neogerris lotus was described from specimens from Manaus, state of Amazonas, northern Brazil (White 1879a). The author did not mention the number of specimens in the type series and did not designate the holotype. Despite being a species with several records in the literature, including redescriptions (e.g., Drake & Harris 1934; Nieser 1970), no author has designated the lectotype for this species. The type series is currently deposited in the Natural History Museum in London (BMNH); this series is composed of three males, two females, and a nymph; all adults are macropterous. Although a female is the only specimen bearing the “Type” label among the five adults, they all also have “ Syntype ” labels. Since males within Neogerris have the diagnostic features hitherto used in species identification, we herein designate one of the males as the lectotype (Figs. 4A–B), and the remaining four adult specimens as paralectotypes.

Discussion. Neogerris lotus and N. celeris are very similar morphologically, a fact already mentioned by Drake & Harris (1934) and Nieser (1994). Nieser (1970) and Nieser & Alkins-Koo (1991) even identified specimens of N. celeris from Brazil and Trinidad and Tobago, respectively, which was later corrected by Nieser (1994); he argued that they were specimens of N. lotus with the pronotum covering the mesonotum. However, Nieser (1994) mentioned that since this condition was probably rare, the two species could still be separated by two diagnostic features: the length of the pronotum and the shape of male abdominal tergum VIII. In N. lotus, the pronotum covers about halfway over the mesonotum (as in Fig. 4E), and the posterior margin of male abdominal tergum VIII is shallowly concave medially (Fig. 5J), whereas in N. celeris, the pronotum almost reaches the metanotum, exposing only a narrow part of the mesonotum (Figs. 4C–D), and the posterior margin of male abdominal tergum VIII is distinctly concave medially, forming a prominent notch (Fig. 5L). After examination of the type series and additional material of N. lotus (including specimens identified by N. Nieser) and paratypes of N. celeris, we noticed that male abdominal tergum VIII is very similar between them. The paratype of N. celeris examined does not have the posterior margin of tergum VIII distinctly notched, unlike the illustrations provided by Drake & Harris (1934: plate XXV, fig. a), but with only a slight median concavity (Fig. 4G).

When studying specimens of Neogerris from Rio Grande do Norte, we detected variation in the shape of male abdominal tergum VIII in one of the collected species (Figs. 5J–L), in addition to a subtle variation in the length of the pronotum, which either completely covered or exposed a thin stripe of the mesonotum. This species was initially identified as N. celeris because the pronotum reaches the metanotum and the posterior margin of male abdominal tergum VIII has a slight median concavity. However, after considering the variation in the pronotal length of N. lotus, and the variation of the posterior margin of abdominal tergum VIII in males from the same locality, which varied from a slight medial concavity, similar to what is described for N. lotus (Figs. 5J–K), to a deeper notch as described for N. celeris (Fig. 5L), led us to re-identify the material. The intraspecific morphological variation described in the literature and that observed in the specimens examined here lead us to consider N. lotus and N. celeris as conspecific. Thus, N. celeris is here considered a junior synonym of N. lotus .

Type material examined. LECTOTYPE of N. lotus: [no locality data] Limnogonus lotus B.W., Pres. by Perth Museum, B.M. 1953-629, Limnogonus lotus B.W. Paratype, Syntype, Paratype, NHMUK 013590048 (♂ macropterous BMNH). PARALECTOTYPES of N. lotus: [no locality data] Limnogonus lotus B.W. Type, Pres. by Perth Museum B.M. 1953-629, Type, Syntype, BMNH (E) #1005960, NHMUK 013590049 (1♀ BMNH); [no locality data] Limnogonus lotus B.W. Paratype, Pres. by J. Ritchie Curator Perth Mus. B.M. 1929-79, on loan from Birt. Mus. det. W.E. China 1932, Paratype, Syntype, NHMUK 013590056 (1♂ BMNH); [no locality data] Limnogonus lotus B.W., Limnogonus lotus B.W. Paratype, Pres. by Perth Museum B.M. 1953-629, NHMUK 013590054, NHMUK 013590055 (1♂, 1♀ BMNH). PARATYPES of N. celeris: PARAGUAY: Villarrica, S.A., Paraguay, 16.3.[19]24, Fran. Schade, Limnogonus celeris D&H, Paratype Limnogonus celeris D&H, CJ Drake Coll. 1956 (1♂, 1♀ apterous USNM).

Additional material examined. BRAZIL, Mato Grosso:Amazonasgebiet, Rio Xingu, Lago Garap, 26.8.[19]65, leg. E.J. Fittkau, coll. Amazonas 196, 0/3,A566-1, Limnogonus lotus White, det. N. Nieser, J. T. Polhemus Collection 2014, C.J. Drake Accession (1♂ apterous USNM); Matto [=Mato] Grosso side of Rio Araguaia, Santa Isabel, VII-15 to 22-57, Borys Malkin, Neogerris lotus (B. White) Det. J.T. Polhemus, J.T. Polhemus Collection 2014 C.J. Drake Accession (1♂ apterous, 5♂, 4♀ macropterous USNM); Capitao Vasconselos, on Rio Tuatuari, Up. Xingu Basin, Matto [=Mato] Grosso, VII-31-1957, Borys Malkin, Neogerris lotus (B. White) Det. J.T. Polhemus, J.T. Polhemus Collection 2014 C.J. Drake Accession (1♂, 1♀ macropterous USNM); Amazonasgebiet, Rio Xingu, Lago Garapu, 26.8.65, leg. E.J. Fittkau, Coll. Amazonas 1960/3, A566-1, Limnogonus lotus White, det. N. Nieser 69’, J. T. Polhemus Collection 2014 C.J. Drake Accession (1♂ apterous, 1♀ macropterous USNM); Amazonasgebiet, Chavantina, Rio d. Mortes, 20.8.65, leg. E.J. Fittkau, Coll. Amazonas 1960/3, A562-2, Limnogonus lotus White N. Nieser det., J. T. Polhemus Collection 2014 C.J. Drake Accession (4♀ macropterous USNM); Amazonasgebiet, Rio Xingu, Rio Sete de S., 24.8.65, leg. E.J. Fittkau, coll. Amazonas 1960 /3, A565-2, Limnogonus celeris D. & Harr. det. N. Nieser 69’, seems to be lotus small!, J. T. Polhemus Collection 2014 C.J. Drake Accession (1♀ apterous USNM). Rio Grande do Norte: Ceará-Mirim, Rio Ceará-Mirim, 5°37’50.4”S, 35°25’16.9”W, 21-IX-2019, R.P. R. Canejo, A.L. Melo leg. (1♂ macropterous CEAAVF); Natal, Rio Pitimbu, EMPARN, 5°55’18.7”S, 35°11’42.4”W, 01-VI-2019, R.P. R. Canejo leg. (3♀ apterous, CEAAVF); Parnamirim, Rio Pitimbu, Vale Encantado, 5°55’56.3”S, 35°10’47.3”W, 17-VII-2022, R.P. R. Canejo leg. (5♂, 7♀ apterous, 1♀ macropterous CEAAVF).