Melloiella truncaticollis De Carlo 1935

Melloiella truncaticollis De Carlo, 1935

(Figs. 11–13)

Melloiella truncaticollis De Carlo, 1935: 2–3 (original description). Discussion. Melloiella truncaticollis was described based on a brachypterous female collected in the state of São Paulo, Brazil (De Carlo 1935). Later, in Brazil, Usinger (1941) and Nieser et al. (1999) recorded this species from the states of Santa Catarina and Rio Grande do Sul, respectively. In Argentina, Lopez-Ruf (1987) and Sites (2022) recorded this species from the province of Misiones. In 2014, the first author of the present study visited the collection of the Museu Nacional of the Universidade Federal do Rio de Janeiro, Rio de Janeiro, and examined the holotype; in 2018, however, a fire destroyed a large part of the entomological collection (Kury et al. 2018), including that holotype.

This species can be easily identified by having the pronotum with lateral margin straight and posterolateral corner truncate, a concolorous dark hemelytra (Fig. 11), body length ca. 15 mm, and subgenital plate with posteromedial margin shallowly concave (Fig. 12I). Here, we examined material from three Brazilian states: Paraná, Santa Catarina, and São Paulo, including macropterous specimens. Males do not have an accessory genitalic process of abdominal tergum VI (Fig. 12A); the medial lobes of abdominal tergum VIII (pseudoparameres) are asymmetrical, subquadrate, and posteromedially directed (Fig. 12B); the phallosoma is elongate, slightly narrowed at mid-length, with the apex rounded (Fig. 12C–D); the endosomal lobes are lightly sclerotized, without spines or teeth, and not papillose (Figs. 12E–G); the parameres are symmetrical, converging medially to a narrowly rounded apex (Fig. 12H)

The genus Melloiella currently contains two species, M. truncaticollis and M. lamprus Nieser, Pelli & Melo, with few records in the literature. So far, only the brachypterous form is known. The macropterous specimens examined here are similar to the brachypterous form, with the following differences: straight posterior margin of the pronotum and the presence of a clavus (including intraclaval suture), embolium, and a developed membrane in the hemelytra (Figs. 11A–B). Unlike other dimorphic species of Naucoridae, in Melloiella the pronotum posterolateral corner of the macropterous specimens is more acute than in the brachypterous form. There is no difference in body length between the two wing forms examined: brachypterous form 13.8–15.3, macropterous form 14.4–15.1.

Distribution. This species is distributed from the Atlantic Forest of southeastern and southern Brazil to northern Argentina. The record for Rio Grande do Sul was provided by Nieser et al. (1999), but without precise locality data (Fig. 13).

Published records. Argentina: Misiones (Lopez-Ruf 1987; Sites 2022). Brazil: Rio Grande do Sul, São Paulo, and Santa Catarina (De Carlo 1935; Usinger 1941; Nieser et al. 1999).

Type material examined. HOLOTYPE ♀ brachypterous (MNRJ) [specimen was destroyed in a fire], [BRAZIL], São Paulo, 18-XII- [1]916, Dr. Costa Lima / Melloiella truncaticollis n. gén, n. sp. De Carlo, Holótipo.

Additional material examined. BRAZIL, Paraná: Morretes, Rio Nhundiaquara, PR11, -25.458027, - 48.834656, 28.x.2023, 14 m, R.P.R. Canejo, J.M.S. Rodrigues, M.S.L. Alexandre & L.D. Pereira cols. (5♂, 1♀ brachypterous, 1♂ macropterous, 1 nymph CEIOC). Santa Catarina: Brasilien, Nova Teutonia, 27°11’B, 52°23’L, Fritz Plaumann, III.1934 / Melloiella truncaticolli [sic] De Carlo Museo Argentino de Ciencias Naturales / Metatypus (1♂ brachypterous MACN). São Paulo: Paranapiacaba, Ponto 2, intermediário, xi.2013 (1♂, 1♀ brachypterous CEIOC); same data, except: Ponto 3, bananal, xi.2013 (1♂ macropterous, 3♀ brachypterous, 1♀ macropterous, 3 nymphs CEIOC); same data, except: Ponto 3, bananal, viii.2013 (2♂ brachypterous, 4 nymphs CEIOC).