Hybobathus arx

Miranda, Gil Felipe Gonçalves, 2017, Revision of the Hybobathus arx and Pelecinobaccha summa species groups (Diptera: Syrphidae), Zootaxa 4338 (1), pp. 1-43 : 4-5

The Hybobathus arx species group

Taxonomic notes. This group was originally separated from other closely related ones by Hull (1949), who named it as Baccha (Aulacibaccha) Hull. It was synonymized by Thompson et al. (1976) under Ocyptamus , and later suggested as the separate H. arx group, part of Hybobathus (previously known as the O. lineatus species group) ( Miranda et al. 2016). It can be distinguished from the other species of Hybobathus by the usually larger size of its species, the scutum pattern made of pale microtrichose vittae and without, or with very sparse, microtrichia laterally ( Hybobathus s. s. has much denser microtrichia, and is very conspicuously microtrichose laterally), and wing dark yellow with a specific paler/hyaline pattern (see diagnosis above). The scutum pattern on this group can clearly be interpreted as derived from the Hybobathus s. s. pattern, however, in the Hybobathus s. s. the microtrichosity is much denser, with the areas without microtrichia being much narrower ( Fig. 1 ). In the species of the H. arx group the posterior anepisternum is usually dark anteriorly, rarely wholly pale (i.e. H. luciane sp. nov.); this character should further help distinguish it from Hybobathus s. s. where the posterior anepisternum is always wholly pale.

The antennal insertions are always separate in the H. arx species group (and apparently in the whole genus). The integument under the widest microtrichose areas of the scutum is pale in some specimens (e.g. USNMENT01288143). The group presents a marked sexual dimorphism where the pile on the vertex/vertical triangle, on the scutum, laterally on the scutellum, on the subscutellar fringe, and on tergite 1 is long and conspicuous on males while being short to inconspicuous on the females. In most cases, females of this group are the only ones with complete sub-lateral vittae on the abdominal tergites, the males having these vittae attenuated to linear/triangular spots; this observation revealed a major issue with Hull’s key (1949) which separated the species of this group based on having, or not, four complete vittae on the abdominal tergites (p. 121, couplet 165).

The hypandrium is very distinct in the H. arx group, having a lateral indentation medially on the ventral notch that extends dorsally, giving the impression that the sclerite is able to fold at that point (e.g. Figs 2g & h ) and its position varying between species [e.g. see in H. arx and H. persimilis ( Curran, 1930) ]. Two specimens were found with a patch of a few pile ventro-laterally on the hypandrium, one identified as H. arx from Brazil and one identified as H. phaeopterus from Mexico (see redescriptions below), which although very unique among the species studied, were from very separate localities and did not seem to represent a separate species. The postgonite in this group is a large, pickaxe-shaped structure, with the dorsal surface extending into an acute dorso-apical corner and with a slight convexity sub-apically, the only exception being H. avittatus sp. nov. that has this surface completely straight all the way to the apex with only a very short and acute projection on the dorso-apical corner ( Fig. 3g ).

Prey records. The prey records for larvae of this group include only species from the families Membracidae and Psyllidae (Hemiptera) ( Table 1 ). In the Hybobathus s. s. there are also records of larvae preying on Thysanoptera ( Rojo et al. 2003).

Key to species. The last key that covered all the species related to the H. arx group ( Hull 1949) relied heavily on the abdominal vittae. By studying the specimens available to me, the central and sublateral markings of the abdominal tergites would vary in length and width in the same series, without any other characters to support the different abdominal patterns as species specific. Thus, they were assumed to vary intraspecifically and other more constant and congruent characters were used to aid in sorting out species (see key below). A picture key is also available at http://keys.inpa.gov.br/?idkey=arxgrp.

1. Abdominal tergites without vittate pattern except for a faint central vitta on tergite 3 ( Fig. 3a ).......... H. avittatus sp. nov.

- Abdominal tergites with pattern of vittae and vittate markings (e.g. Fig. 5b )....................................... 2

2. Abdominal segment 2 rectangular, between 2 and 3.5 (rarely 4) times as long as smallest width ( Figs 2b and 6a ).......... 3

- Abdominal segment 2 long, more than 4.5 times as long as smallest width ( Fig. 5b )................................. 4

3. Abdominal tergite 2 between 3 and 4 times as long as smallest width ( Fig. 2b ); male scutum with short and dark pile ( Fig. 2f ); female segment 6 with vittate pattern ( Fig. 2c ).................................................... H. arx (Fluke)

- Abdominal tergite 2 less than 2.5 times as long as smallest width ( Fig. 6a ); male scutum with long and white pile ( Fig. 6d ); female segment 6 without distinct vittate pattern ( Fig. 6f )........................... H. persimilis (Curran) comb. nov.

4. Pleuron wholly yellow, at most only ventro-posterior margin of katatergum black, but pleuron might have slightly reddish/ orange areas ( Fig. 4g ); male tergite 1 with short appressed pile ( Fig. 4e ); female posterior row of the mesofemur with appressed pile ( Fig. 4f )................................................................... H. luciane sp. nov.

- Pleuron distinctly black at least on ventro-posteiror margin of katatergum and anterior 1/3 of posterior anepisternum ( Fig. 7g ); male tergite 1 with long erect pile ( Fig. 7b ); in female, posterior row of the mesofemur with erect pile.................. 5

5. Face with medial dark vitta or at least slightly darker on the sides of the tubercle ( Fig. 5c ); frons with wide dark central vitta, and microtrichosity differently oriented dorsally (appearing as a dull patch); frontal triangle with large dark triangular marking ( Fig. 5e ); scutum pile pale in male.............................................. H. obsoletus (Curran) comb. nov.

- Face wholly yellow; frons at most with narrow dark central vitta ( Fig. 7f ) that might expand slightly anteriorly, and microtrichosity all in the same direction (without a dull patch); frontal triangle wholly yellow ( Fig. 7d ) or at most with small, dark, central, diamond-shaped marking ( Fig. 7e ); scutum pile mostly dark in male............... H. phaeopterus (Schiner)

Figures

FIGURE 1. Schematic drawing of the microtrichosity pattern on the scutum of the Hybobathus sensu stricto (left) and Hybobathus arx species group (right).

FIGURE 2. Hybobathus arx (Fluke, 1936). a. Male, holotype, habitus, dorsal (photo courtesy AMNH). b. Female, habitus, dorsal. c. Female, abdominal segments 5 and 6, dorsal. d. Male, head, dorsal. e. Male, head, oblique frontal. f. Female, scutum, oblique lateral. g – i. Male, genitalia: g. Genitalia, lateral. h. Hypandrium, ventral. i. Epandrium, ventral. j – m. Female, genitalia: j. Dorsal. k. Ventral. l. Apex, dorsal. m. Apex, ventral. bph: Basiphallus, drk: Dark markings on the face, ep: Epiproct, ind: Ventro-lateral indentation of the hypandrium, pgt: Postgonite, sscl: Subepandrial sclerite, s 2: abdominal segment 2, sct: Scutellum, srs: Surstylus, tg 6: abdominal tergite 6, trvs: Transverse suture.

FIGURE 3. Hybobathus avittatus sp. nov., male, holotype. a. Habitus, dorsal. b. Habitus, lateral. c. Head, frontal. d – h. Genitalia: d. Epandrium, dorsal. e. Epandrium, ventral. f. Hypandrium, ventral. g. Hypandrium, lateral. h. Hypandrium, basiphallus focus, lateral. bph: Basiphallus, ind: Ventro-lateral indentation of the hypandrium, pgt: Postgonite, sscl: Subepandrial sclerite, srs: Surstylus.

FIGURE 4. Hybobathus luciane sp. nov. a. Male, holotype, habitus, dorsal. b. Male, holotype, habitus, lateral. c. Female, habitus, lateral. d. Female, habitus, dorsal. e. Male, holotype, abdominal segment 1, dorsal. f. Female, mesofemur, oblique dorsal. g. Male, pleuron, lateral. h – j. Puparium: h. Posterior respiratory process, dorsal. i. Posterior respiratory process, anterior. j. Habitus, lateral. k – m. Male genitalia: k. Hypandrium, ventral. l. Genitalia, lateral. m. Epandrium, ventral. n – p. Female genitalia: n. Dorsal. o. Ventral. p. Lateral. bph: Basiphallus, cerc: Cercus, ep: Epiproct, panepst: Posterior anepisternum, pgt: Postgonite, sscl: Subepandrial sclerite, spr: Spiracular opening, srs: Surstylus.

FIGURE 5. Hybobathus obsoletus (Curran, 1941) comb. nov. a. Male, Baccha nectarina holotype, habitus, dorsal [copyright President and Fellows of Harvard College (MCZ)]. b. Female, abdomen, dorsal. c. Female, head, frontal. d. Female, head, dorsal. e. Male, Baccha obsoleta holotype, head, oblique dorsal (photo courtesy AMNH). f – i. Male genitalia: f. Epandrium, lateral. g. Epandrium, ventral. h. Hypandrium, lateral. i. Hypandrium, ventral. j – m. Female genitalia: j. Dorsal. k. Apex, dorsal. l. Ventral. m. Lateral. bph: Basiphallus, cerc: Cercus, drk: Dark marking on the face, ep: Epiproct, ind: Ventro-lateral indentation of the hypandrium, pgt: Postgonite, sscl: Subepandrial sclerite, s 2: abdominal segment 2, srs: Surstylus.

FIGURE 6. Hybobathus persimilis (Curran, 1930) comb. nov. a. Male, holotype, habitus, dorsal (photo courtesy AMNH). b. Male, habitus, lateral. c. Female, habitus, dorsal. d. Male, scutum, lateral. e. Female, head, frontal. f. Female, abdominal segments 5 and 6, dorsal. g – j. Male genitalia: g. Epandrium, lateral. h. Hypandrium, lateral. i. Hypandrium, ventral. j. Epandrium, ventral. k – n. Female genitalia: k. abdominal segment 7, dorsal. l. abdominal segment 7, lateral. m. abdominal segment 8 and proctiger, lateral. n. abdominal segment 8 and proctiger, dorsal. bph: Basiphallus, conc: Concavity on the apical margin of the postgonite, conv: Apico-medial convexity of the subepandrial sclerite, crc: Cercus, drk: Dark marking on the face, ep: Epiproct, ind: Ventro-lateral indentation of the hypandrium, pgt: Postgonite, sscl: Subepandrial sclerite, s 2: abdominal segment 2, srs: Surstylus, tg 6: abdominal tergite 6, trvs: Transverse suture.

FIGURE 7. Hybobathus phaeopterus (Schiner, 1868). a. Male, lectotype, habitus, dorsal (courtesy NHMW). b. Male, abdominal tergite 1, dorsal. c. Female, habitus, dorsal. d. Male, lectotype, head, dorsal (courtesy NHMW). e. Male, paralectotype, head, dorsal (courtesy NHMW). f. Female, paralectotype, head, dorsal (courtesy NHMW). g. Female, anepisternum, lateral. h. Female, detail of dorsal occiput, oblique dorsal. i – l. Male genitalia: i. Epandrium, dorsal. j. Epandrium, ventral. k. Hypadrium, lateral. l. Hypandrium, ventral. m – o. Female genitalia: m. Dorsal. n. Ventral. o. Lateral. aanepst: Anterior anepisternum, bph: Basiphallus, cerc: Cercus, ep: Epiproct, oc: Occiput, panepst: Posterior anepisternum, pgt: Postgonite, sscl: Subepandrial sclerite, s 2: abdominal segment 2, srs: Surstylus.

Tables

TABLE 1. Known prey records for the Hybobathus arx species group.

Species	Prey	Reference
Hybobathus arx	Antianthe expansa (Germar) ( Hemiptera , Membracidae )	Montoya & Pérez (2009)
H. luciane	Membracis foliata (Linnaeus) ( Hemiptera , Membracidae )	This study
H. persimilis	Tuthillia cognata Hodkinson, Brown & Burckhardt ( Hemiptera , Psyllidae )	Pérez & Iannacone (2009)
H. phaeopterus	Guayaquila xiphias (Fabricius) ( Hemiptera , Membracidae )	This study