Description of the males of Lincus singularis and Lincus incisus ( Hemiptera : Pentatomidae : Discocephalinae )

The Neotropical Lincus Stål, 1867 includes 35 species, thirteen of which are known only from females. Several species are vectors of Phytomonas staheli McGhee & McGhee, 1979, a trypanosomatid parasitic in palm-trees in South America that causes hart-rot, sudden and slow wilt diseases. The hitherto unknown males of L. singularis Rolston, 1983 (“swollen head” species group found in the oil palm Elaeis guineensis Jacq.), and L. incisus Rolston, 1983 (“hatchetlobed” species group; found in the coconut tree Cocos nucifera L.), are described with emphasis on the morphology of the genitalia, and taxonomic remarks are provided. Males of L. singularis can be distinguished from other species included in “swollen head” group by their pronotal lobes with anterior and posterior margins subparallel and projected laterally from the eye margin, while males of L. incisus can be distinguished from the species of the “swollen head” group by an obtuse projection with a deepest incision and several additional diagnostic characters of the genitalia.

Lincus Stål, 1867 is the richest genus of Ochlerini, comprising 35 species (CAMPOS & GRAZIA 2006).Even though the genus was described in the 19th century (STÅL 1867), most of its 25 species were described in the late 20th century (ROLSTON 1983, 1989, DOLLING 1984), and 13 of them are known only from one sex (ROLSTON 1983).Species of Lincus are found mostly in the Amazon region.There are a few exceptions to this, for instance Lincus lobuliger Breddin, 1908, recorded from the Brazilian Atlantic Forest and Lincus anulatus Rolston, 1983 andLincus discessus (Distant, 1900) from Central America (ROLSTON 1983).Several species are sympatric in different countries.Geographic records of Lincus are particularly rich in Peru due to the extensive surveys on native palms carried out during the 1980's (COUTURIER & KAHN 1989, 1992, LLOSA et al. 1990).Sixteen species occur in that country, including Lincus singularis Rolston, 1983, although it has never been collected on Elaeis guineensis Jacq.Suriname comes next in terms of species richness in the Amazon region (ROLSTON 1983, 1989, DOLLING 1984), with six species, including Lincus incisus Rolston, 1983.
The association of pentatomids with the transmission of Phytomonas staheli McGhee & McGhee, 1979, a trypanosomatid parasitic in plants, has been known for a long time and is well documented (for a review see CAMARGO 1999 andMITCHELL 2004).Several species of Lincus play a major role as vectors of hart-rot, and of sudden and slow wilt (also called Marchitez sorpresiva in Spanish-speaking countries) diseases in palm trees (Arecaceae) in South America, being of economic interest in crops of E. guineensis (African oil palm) and Cocos nucifera L. (coconut) (DESMIER DE CHENON 1984, COUTURIER & KAHN 1989, PERTHUIS et al. 1985, PANIZZI et al. 2000, DI LUCCA et al. 2013; for a review see HOWARD 2001).Although eleven species of Lincus have been reported on palm trees (HOWARD 2001), the genus was not listed as a possible vector of oil palm diseases until the 1980's (COUTURIER & KAHN 1992).Furthermore, transmission of Phytomonas trypanosomatids to palms has been documented in only six species, four of which transmit the parasite to E. guineensis: Lincus lethifer Dolling, 1984, L. lobuliger, Lincus tumidifrons Rolston, 1983, and Lincus spurcus Rolston, 1983(CAMARGO 1999, DI LUCCA et al. 2013).
In 2009, the corresponding author received, for identification, specimens of Lincus collected from E. guineensis palm trees from Palmas del Espino S.A., Peru.These specimens were identified as L. spurcus and L. singularis, and included the only known males of the latter.Moreover, during the course of this study, we located males of L. incisus among specimens of Ochlerini received during the 1990's, two of which from C. nucifera crops cultivated by Sococo S.A., Moju, Pará State, Brazil.For the first time, L. singularis and L. incisus are reported from oil palm and coconut trees, respectively, and their males are described and illustrated for the first time, with emphasis on the morphology of genitalia.1983 ("swollen head" species group found in the oil palm Elaeis guineensis Jacq.), and L. incisus Rolston, 1983 ("hatchetlobed" species group; found in the coconut tree Cocos nucifera L.), are described with emphasis on the morphology of the genitalia, and taxonomic remarks are provided.Males of L. singularis can be distinguished from other species included in "swollen head" group by their pronotal lobes with anterior and posterior margins subparallel and projected laterally from the eye margin, while males of L. incisus can be distinguished from the species of the "swollen head"

Description of the males of
group by an obtuse projection with a deepest incision and several additional diagnostic characters of the genitalia.KEY WORDS.Genitalia; morphology; Ochlerini; stink bugs; taxonomy.

MATERIAL AND METHODS
Five males and one female of L. singularis and three males and three females of L. incisus were examined in this study.The species were identified based in a revision by ROLSTON (1983).Observation of specimens, dissection and preservation followed GARBELOTTO et al. (2013).Measurements are in millimeters (mm) and follow mainly GARBELOTTO et al. (2013) and ROLSTON (1983) for: length and width of eye and pronotal lobe, and interocellar distance.The terminology of BAKER (1931), DUPUIS (1970), CAMPOS & GRAZIA (2006) and GARBELOTTO et al. (2013) were adopted for genitalic structures.Photographs were taken using a Nikon AZ100M stereomicroscope and NIS-Elements Advanced Research software.Drawings were made under a stereomicroscope Leica MZ12 coupled with camera lucida and were vectored using Adobe Illustrator.Whenever possible, collection data were georeferenced following GARBELOTTO et al. (2013); coordinates are in decimal degrees.
Collections' acronyms follow EVENHUIS (2014).Voucher specimens are deposited in the entomological collection of the Departamento de Zoologia at Universidade Federal do Rio Grande do Sul (UFRG), Porto Alegre, RS, Brazil.
Distribution.Peru, Cusco and San Martín regions.
Remarks.Although no phylogenetic hypothesis has been advanced for species of Lincus, the genus was recovered in the Herrichella Distant, 1911 clade in a cladistic analysis of the Ochlerini (CAMPOS & GRAZIA 2006).The relationship between Lincus and the other members of the clade, however, remained unresolved.More recently, the genus (represented by L. lobuliger) was recovered as the sister group of the remaining taxa of the Herrichella clade in the phylogenetic analysis of GARBELOTTO et al. (2013).The monophyly of the genus, however, remains to be tested.Several species of Lincus are recognizable by their well-developed pronotal lobes, and all known males have tubular proctiger and reduced parameres (ROLSTON 1983(ROLSTON , 1992)).These characters were not used in the phylogenetic studies mentioned above.Regarding the phylogenetic relationships among the species of Lincus, ROLSTON (1983) placed L. singularis along with Lincus parvulus (Ruckes, 1958) and L. tumidifrons in the "swollen head" informal group of species ("species group of convenience" sensu ROLSTON 1983).This group was characterized by having a tumid vertex.Some features of the pygophore of L. singularis are consistent with Rolston's proposal to place the species in it, e.g. the 'V' shape of the ventral rim of the pygophore; subrectangular proctiger with acute apex; and globose phallotheca, the latter also observed in L. tumidifrons.Lincus singularis can be differentiated from the other species in the "swollen head" group by having the anterior and posterior margins of the pronotal lobes subparallel and each lobe projected laterad of its corresponding eye; the vertex of head not as tumid as in L. parvulus and L. tumidifrons (Fig. 1; for L. parvulus and L. tumidifrons see ROLSTON 1983, Figs. 30 and 36); and the ventral opening of the pygophore is narrower than in those species (Fig. 3, vr; for L. parvulus and L. tumidifrons see ROLSTON 1983, Figs. 32 and 41).