Chorosomella, HORVATH, 1906

Tatarnic, Nikolai J. & Cassis, Gerasimos, 2012, The Halticini of the world (Insecta: Heteroptera: Miridae: Orthotylinae): generic reclassification, phylogeny, and host plant associations, Zoological Journal of the Linnean Society 164 (3), pp. 558-658 : 582-585

CHOROSOMELLA HORVÁTH ( FIGS 3 , 13–14 )

Chorosomella Horváth, 1906: 545 (gen. nov.; type species: Chorosomella jakowleffi Horváth, 1906 by monotypy); Carvalho, 1959: 283 (cat.); Kerzhner,

1962: 385 (tribal placement); Wagner, 1973: 107 (description); Schuh, 1995: 46 (cat.)

Diagnosis: Chorosomella is distinguished from all other halticines by the following combination of characters: gracile body; elongate appendages; rectangulate head; frons with conical projection; vertex with midline sulcus; bucculae narrow; eyes distant from anterior margin of pronotum; AI greatly elongate and thick; labium short, reaching mesocoxae; MTG external efferent system obsolete; pretarsi with pulvilli; single elongate endosomal spicule.

Redescription: Male macropterous, female micropterous. Coloration ( Fig. 3 ): pale yellow-brown. Surface and vestiture ( Figs 3 , 13A–D ): smooth, almost glabrous. Antennae clothed in very short adpressed spinose setae, becoming most dense on AII through AIV; femora with very short, adpressed spinose setae primarily on dorsal surface; tibiae with slightly longer, semi-erect spine-like setae, shorter than leg width. Structure: head ( Figs 3 , 13A, B ): rectangulate, elongate, length greater than head height; vertex flat with thin medial longitudinal sulcus, posterior margin not carinate; frons with conical projection, extending beyond clypeus; posterior margin of eyes removed from anterior margin of pronotum; genae height subequal to eye height; mandibular and maxillary plates small; bucculae extremely narrow; antennae ( Figs 3 , 13A, B ): inserted at eye midheight; elongate, slender, longer than body; AI thickest, longer than head and pronotum combined; AII approximately twice as long as AI; AIII slightly longer than first; AIV short. Labium ( Fig. 13A, B ): short, nearly reaching mesocoxae. Thorax ( Figs 3 , 13A–D ): pronotum narrow, trapezoidal, posteriorly only slightly wider than anterior margin, nearly flat, collar absent, callosite region distinct, lateral margins rounded, posterior margin medially concave; mesoscutum elongate; scutellum short, apex blunt, rounded; metathoracic spiracle a thin slit, with evaporative bodies along posterior margin, MTG external efferent system obsolete. Hemelytra ( Fig. 3 ): males macropterous, costal margin concave, becoming very narrow towards apex; membrane with single cell, apex reaches abdominal tergite VII, minor cell obsolete; females micropterous, hemelytra translucent; without cuneal fracture or membrane; only reaching abdominal tergite III. Legs ( Figs 3 , 13A, B, E ): very long, cylindrical, thin; pretarsi with fleshy pulvilli. Abdomen ( Fig. 1 ): elongate in both sexes. Male genitalia ( Fig. 14A–C ): pygophore elongate, posterior margin laterally with pair of caudally projecting processes; parameres roughly equal in size; left paramere narrow, weakly bent, weakly concave, apex of apophysis bifid; right paramere weakly concave, without apical apophysis; phallotheca elongate, narrow and simple, apically slender; ductus seminis elongate, very thin; secondary gonopore weakly sclerotized, opening into elongate tubular spine-like spicule, reaching apex of phallotheca. Female genitalia ( Fig. 14D ): sclerotized rings thin, elongate, ribbon-like, very weakly sclerotized. DVP and VLP membranous, without sclerotization; posterior wall of bursa copulatrix entirely membranous, without processes or modifications vestibular region symmetrical. Vestibular region symmetrical, very weakly swollen, with margins wrinkled and membranous, converging anteriorly.

Diversity and distribution: Chorosomella is comprised of two species from central districts of the Palaearctic region, including the Russian Crimea and Kazakhstan.

Included species: Chorosomella horvathi Kiritshenko, 1911 Kazakhstan

Chorosomella jakowleffi Horváth, 1906 * Russia

Biology and host plant associations: Chorosomella jakowleffi is known to breed and feed on grasses ( Kerzhner & Yachevskii, 1967; Wagner, 1973; Schuh & Lattin, 1980) ( Table 1).

Remarks: Chorosomella was previously placed in the Mirinae : Stenodemini ( Horváth, 1906) based on superficial similarities, such as the elongate body and appendages, synonymous with many grass-feeding true bugs. Reuter (1910) transferred the genus to the Orthotylini , but Carvalho (1952) subsequently restored it to the Stenodemini . Kerzhner (1962) first moved Chorosomella to the Halticini , whereas Wagner (1973) regarded the halticines as a subfamily, and erected a new tribe for Chorosomella : the Chorosomellini. Most authors follow Kerzhner (1962), who based his decision on various characters he considered typical of the Halticini : L-shaped left paramere, spoon-shaped right paramere, membranous aedeagus with spicula, and tall genae, and supported by their close relationship with graminoids. In examining Chorosomella we find that some of these character evaluations are disputable; compared to other Halticini the left paramere is much less angular; the secondary gonopore is unlike that of any other Halticini , and the genae are considerably shorter. Additionally, the long, gracile body shape, long thin legs, pale coloration, the unique shape of the head, and the structure of the female genitalia, particularly the sclerotized rings, are also unlike all other Halticini .

In our unweighted phylogenetic analysis Chorosomella groups with Dimorphocoris and Compositocoris ( Fig. 1 ) by several homoplasies, including an overall nonblack coloration (1-0), a slightly elongate head (10-1), and the extreme brachyptery of females, with the wings reduced to wing pads (37-3). However, under implied weighting this relationship dissolves, with Chorosomella now appearing as sister to Plagiotylus in a clade that also includes Strongylocoris . This clade is supported by the lack of metathoracic evaporative area (24-0) and the extreme reduction of the metathoracic scent gland itself (23-0). Based on the current data it is unclear which of these competing topologies more closely reflects the true placement of Chorosomella .

COMPOSITOCORIS SCHWARTZ, SCHUH & TATARNIC

( FIGS 3 , 15–16 )

Compositocoris Schwartz, Schuh & Tatarnic, 2008: 23 (gen. nov.; type species: Compositocoris senecionus Schwartz et al., 2008 by original designation)

Diagnosis: Compositocoris is recognized by the following combination of characters: strongly sexually dimorphic, males macropterous and elongate, females ovoid and micropterous; bright green coloration; females with apically stellate bristle-like setae; medial margins of first gonapophyses forming vestibular opening symmetrical and weakly sclerotized. This genus is very similar to Dimorphocoris but is distinguished by the shorter genal height, coloration, and the apically stellate setae of the females.

Diversity and distribution: Compositocoris is a monotypic genus, known only from Namaqualand, South Africa.

Included species: Compositocoris senecionus Schwartz et al., 2008 * South Africa

Biology and host plant associations: This species is known from numerous species of asterids belonging to the genera Senecio, Leyesera , and Ursinia (Asteraceae) ( Table 1).

Remarks: Compositocoris is very similar to Dimorphocoris in many aspects, including overall male and female body form, the presence of paddle-like sclerites apical to the secondary gonopore, and the patches of honeycombed texturing on the head and thorax (2-1: the only unambiguous synapomorphy linking these as sister taxa in our phylogeny). Only the bright coloration, shorter head, and stellate bristle-like setae in the female distinguish Compositocoris . A more thorough examination of Dimorphocoris is necessary to identify the range of morphological variation and to determine if Compositocoris is congeneric; this was beyond the scope of this study, as we only had access to a few species of the speciose Dimorphocoris .

Figures

Figure 1. Strict consensus of three equally parsimonious trees under equal weighting. Numbers above branches are jackknife support (36% removal probability, values below 50% not shown); numbers below are Bremer support values.

Figure 3. Photographs of Halticini genera: Acratheus–Halticus. Abbreviations: F, female; M, male.

Figure 13. Scanning electron micrograph images of Chorosomella jakwoleffi (male). A, body, lateral view; B, head and thorax, lateral view; C, meso- and metathorax, lateral view; D, meso- and metathorax, detail; E, tarsus.

Figure 14. Male and female genitalia of Chorosomella jakowleffi. A, aedeagus; B, left paramere; C, right paramere; D, vestibulum; E, bursa copulatrix, dorsal view. Abbreviations: SC, seminal conceptacle; SR, sclerotized ring.

Figure 15. Scanning electron micrograph images of Compositocoris senecionus (male and female). A, head of female, dorsal view; B, head and prothorax of female, lateral view; C, head of male, dorsal view; D, meso- and metathorax of male, lateral view; E, external efferent system of the metathoracic scent gland, detail; F, dorsum of female, showing apically stellate setae; G, detail of apically stellate seta; H, pygophore. Modified from Schwartz et al. (2008).

Figure 16. Male and female genitalia of Compositocoris senicionus. A, detail of secondary gonopore and endosoma; B, aedeagus; C, left paramere; D, right paramere; E, detail of sclerotized ring, dorsal view; F, first gonapophyses, ventral view; G, posterior wall. Modified from Schwartz et al. (2008).