This contribution describes and illustrates the male genitalia of two new species of Blaberidae collected in the state of Minas Gerais, Brazil: T. caldensis sp. n. resembles T. neospectrum Lopes, 1978, differing in the coloration, size and genitalia; and T. morroferrensis sp. n., which resembles T. guttulosum (Walker, 1868) but also differs in the size and coloration of specimen and genital pieces morphology. The genital plates were removed after dissection of the posterior part of the abdomen, and were stored in microvials containing glycerin, attached to the respective exemplar in the collection of the Museu Nacional of Rio de Janeiro, Brazil. A key to males of the species of the genus is also presented. Illustrations of T. neospectrum and T. guttulosum are provided to clarify the comparisons with the new species described here.

Blattodea , genitalia, key, new species, taxonomy

The genus Tribonium was described by Saussure (1862), who designated Blatta spectrum Eschscholtz, 1822 as the type species. Originally, Saussure described the genus as encompassing species with the following characteristics: antennae slightly longer than body; pronotum transverse; supranal plate of male enlarged; cerci short; coloration brown with scattered black spots, mainly on tegmina. Species identification within the genus is difficult, requiring morphological studies of the genitalia. Saussure described Tribonium in a key, where he separated the genus from Proscratea Burmeister, 1838, which is characterized by a shorter antenna, not reaching beyond apex of abdomen; pronotum with apical margin sinuous; tegmina broad; and sides of abdomen and extremities elevated. Saussure (1864) redescribed the genus and provided additional diagnostic characters: dilated in general shape; abdomen significantly widened, dorsoventrally flattened, with serriform ridges; subgenital plate with short styles.

Brunner von Wattenwyl (1865) described the genus Philobora, which was later synonymized with Tribonium, and characterized it by the head facing down, with vertex exposed; pronotum shaped as lid over the head, with dorsal margin forming an obtuse angle; tegmina wide basally; scapular area with folded comb; anal field triangular; wings rounded, with median vein complete; legs sturdy; abdomen flattened.

Hebard (1933) described a new species of Tribonium from Colombia: Tribonium colombicum.

Princis (1964) cataloged five species, recording the genus from Brazil, Argentina, Paraguay, Bolivia and Colombia.

Roth (1970) quoted Rehn (1932) as stating that “the genera Zetobora, Lanxoblatta, Zetoborella, and Schizopilia ... are clearly derivatives of a single phylum,” whereas Schistopeltis and Tribonium “.... typifies a distinct and clearly marked phylogenetic series.” In general, the structure of the male genitalia tends to support Rehn’s hypothesis. However, Roth separated Zetobora from the other three genera of his grouping because of the “relatively poorly developed L2d”, and described the genitalia of some species of Tribonium, which he assigned to the subfamily Zetoborinae. He characterized the genitalia of the genus as having the anterior portion of the median sclerite well developed, extended dorsally, with posterior portion extended upward; and subapical incision of right phallomere well defined at middle of hook.

In a footnote, Roth (1974) made corrections to the figures of T. conspersum (Guérin-Méneville & Percheron, 1835) and T. spectrum (Eschscholtz, 1822) that he had published (Roth 1970).

Roth (1974) suggested that Tribonium is not closely related to Schistopeltis Rehn, 1916, and separated the former based on the uniformly rounded shape of the pronotum. In Schistopeltis the pronotal margin is tapered and cropped dorsally.

Lopes (1978) revised Tribonium, and diagnosed the genus with the following characters: triangular head with interocular space less than distance between antennae, ocelli present; maxillary palps well developed; tegmina with marginal field extended; veins numerous and irregular; wings with marginal field narrow, subcostal vein reaching basal third of scapular field; cubital vein with numerous complete and few incomplete veins, apical triangle absent; fore femur with row of tiny spines on anteroventral margin; pulvilli well developed; claws symmetrical and without specializations; arolia moderately developed; supra-anal plate cordiform, symmetrical, subgenital plate asymmetrical, with digitiform styles.

Lopes (1978) mentioned that the genus is essentially Neotropical, with its species having an overall brown coloration with scattered black spots, mainly on the tegmina; and that the general similarities make species identification difficult, and further morphological studies of the genitalia are needed. Lopes (1978) added that members of Tribonium are distributed from French Guiana, Colombia, Brazil, Bolivia, and Paraguay to Argentina.

Grandcolas (1993) included Tribonium in his phylogenetic study of the subfamily Zetoborinae, and described the species Tribonium guyanense based on a female. Roth (2003) listed the species that had been described after the publication by Princis (1964), and supported the idea that the genus belongs in Zetoborinae.

Lopes and Silva (2010) described a new species from the state of Amazonas, Brazil, contributing to the understanding of the genus and its geographical distribution.

Valverde et al. (2012), in their morphological study of individuals belonging to Schistopeltis lizeri Rehn, 1928, commented on their similarity with species of Tribonium, from which they differ in the configurations of the median sclerite and the pronotum.

Eight of the 11 presently known species are from Brazil: T. conspersum (Guérin & Percheron), T. conspurcatum (Burmeister), T. delicatum Lopes, T. elegans (Brunner), T. guttulosum (Walker), T. litoris Lopes, T. neospectrum Lopes, and T. spectrum (Eschscholtz).

In this contribution two new species of Tribonium are added, from the state of Minas Gerais, Brazil, and present illustrations of their internal genitalia and a key for the available males of the genus. T. guyanense, T. conspurcatum, and T. elegans are not included in the key because they were described based only on females.

The type species (T. spectrum) was not used in the key because the description by Saussure provides few morphological characters. Unfortunately, we received no response to our request for the loan of the type material, because of the absence of a researcher in the Moscow Museum where it is deposited. Tribonium colombicum was not examined because the Philadelphia Academy of Natural Sciences failed to respond to our request for the loan of the specimen deposited under number 1215. It is necessary to include color characters in the key, because these are essential for the identification of species of Tribonium, as is the shape of the genitalia.

The genital plates were removed after dissection of the posterior part of the abdomen, using traditional dissection techniques as described by Lopes and Oliveira (2000). After analysis, the genital plates and pieces were stored in microvials containing glycerin, and attached to the respective exemplar, a procedure developed by Gurney et al. (1964). The terminology for the genitalia and the taxonomic classification follow Roth (2003). The specimens were also compared with other specimens of Tribonium deposited in the Blattodea Collection of the Museu Nacional of Rio de Janeiro (MNRJ), and with descriptions in the literature.

After observation and comparison of specimens of different species of Tribonium under the stereomicroscope, distinguishing characteristics were selected for use in the key.

The holotypes are deposited in the collection of the Department of Entomology at the Museu Nacional of Rio de Janeiro (MNRJ).

To Dr. Janet W. Reid for editing the text in English.