Abstract
The monotypic genus Sturmiodexia Townsend, 1919 is a poorly known Neotropical taxon. Herein a new generic synonymy is proposed for this genus: Platyrrhinodexia Townsend, 1927 syn. nov. Two new combinations are assigned for Sturmiodexia: S. moyobambensis (Townsend, 1929) comb nov. and S. punctulata (Townsend, 1927) comb nov. Redescriptions were done for S. punctulata, S. rubescens Townsend 1919 and S. muscaria (Walker 1853). With these new propositions, Sturmiodexia is left with four species. In addition, the male and female terminalia, and the first instar larva, are described and illustrated for the first time for S. punctulata. Finally, a diagnose for Sturmiodexia and a key to all species is given.
Introduction
Sturmiodexia Townsend, 1919 is Neotropical genus currently known from its type species described from Peru, S. rubescens, Townsend, 1919 and by one species formerly considered as Ptilodexia Brauer & Bergenstamm, 1889, that is now placed in Sturmiodexia by O’Hara et al. (2020), S. muscaria (Walker 1853). This genus is placed in Dexiini (Dexiinae) by O’Hara et al. (2020), the largest tribe of Dexiinae with 129 genera, of which, 73 have a Neotropical distribution. Considering the Neotropical taxa, 43 genera are monotypic, and the majority of those genera were never comparatively studied, with the only keys available being from Townsend in his Manual of Myiology, a 12-volume series on the “Oestromuscaria” published between 1934–1942, a work that is regarded as incomprehensible, unmanageable, and artificial (Mesnil 1980; O’Hara 2013). Hence, the identification of the Neotropical Dexiini is very difficult, constituting a real taxonomic impediment. In order to reach to an approximation of a correct generic identification, one needs to cross-check among existing identification keys and other resources (Santis 2020), often prepared for other regions (e.g., Wood & Zumbado 2010). In relation to a specific identification, the scenario is even worse; Townsend’s Manual of Myiology and the keys contained in the regional manuals of Diptera cannot be of any help. Accordingly, the lack of species keys is another example of the problems for the identification of Neotropical Dexiini. A straightforward example of this trend is Sturmiodexia that was last studied by Townsend (1938), in which he redescribed this genus, and was never comparatively studied. Thus, after its initial description, references to this genus appeared in the literature only through lists (O’Hara et al. 2020) and catalogues (Guimarães 1971).
The present work intends to overcome these difficulties by presenting: Platyrrhinodexia Townsend 1927 as a syn. nov., for Sturmiodexia, with S. moyobambensis (Townsend 1929) comb nov. and S. punctulata (Townsend 1927) comb nov., with the first description and illustration of the male and female terminalia and the first instar larval redescription of S. punctulata (Townsend 1927); in addition redescriptions, diagnosis and photographs are provided for S. rubescens Townsend 1919, and S. muscaria (Walker 1853) and finally, a diagnosis for Sturmiodexia and a key to all four the species is given.
Material and methods
The examined material is deposited at the MNRJ, Museu Nacional do Rio de Janeiro, Rio de Janeiro, Brazil; MZSP, Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil and NHMUK, Natural History Museum, London, UK. Additional depositories cited in the text: USNM, Smithsonian National Museum of Natural History, Washington, D.C., USA. The label data are presented within quotation marks for each label, with forward slashes indicating line breaks and semicolons separating different labels. Comments about labels, additional information and corrections are given in square brackets.
Morphological terminology followed Cumming & Wood (2017). The terminology of first-instar larvae followed the nomenclature used by Cantrell (1988), but the term ‘cephaloskeleton’ of Courtney et al. (2000) was used. For the study of male terminalia, the abdomen was dissected from the fourth segment. Photographs of the pinned specimens were taken using a Canon EOS 5D DSLR camera for the material deposited at NHMUK, a Leica MC170 HD digital camera attached to a Leica MZ16 stereomicroscope for the MZSP material. The images were subsequently stacked (merging different focal planes into one image) with the software Helicon Focus 7.5.8. and edited in Adobe Photoshop CC 2019. Illustrations were made using a camera lucida attached to a Leica MZ16 stereomicroscope, and edited and arranged in Adobe Illustrator CC 2019.
To digest tissues and clarify structures, the last abdominal segments were put into a glass tube containing a 10% KOH solution and heated in boiling water for 5 minutes, neutralized in a 5% acetic acid solution and rinsed in distilled water. After examination, the dissected parts were placed in glycerin inside a plastic microvial pinned with the source specimen.
Results
Genus Sturmiodexia Townsend, 1919
Sturmiodexia Townsend 1919: 549. Type species: S. rubescens Townsend 1919 (original designation).
Platyrrhinodexia Townsend 1927: 228. Type species: P. punctulata Townsend 1927 (original designation). Syn. nov.
References. Townsend (1936: 137, diagnosis of adults and immatures of Prosenini, including Platyrrhinodexia and Sturmiodexia); Townsend (1938: 362, redescription of Platyrrhinodexia; 377, redescription of Sturmiodexia); Guimarães (1971: 32, Platyrrhinodexia; 35, Sturmiodexia, catalog); Evenhuis et al. (2015: 220, Platyrrhinodexia; 255, Sturmiodexia, catalog of Townsend’s genera); O’Hara & Henderson (2020: 63, Platyrrhinodexia; 72, Sturmiodexia, World checklist of tachinid genera); O’Hara et al. (2020: 64, Platyrrhinodexia; 77, Sturmiodexia, World checklist of tachinid species).
Included species:
S. moyobambensis (Townsend 1929: 366) (Platyrrhinodexia). Holotype male: Peru, Moyobamba (USNM, holotype not examined). Comb. nov.
S. muscaria (Walker 1853: 308) (Dexia). Male holotype: “Brazil” (NHMUK, holotype examined).
S. punctulata (Townsend 1927: 228) (Platyrrhinodexia). Holotype male: Brazil, São Paulo, Itaquaquecetuba (USNM, holotype not examined; male paratype, MZSP, examined). Comb. nov.
S. rubescens Townsend 1919: 550. Holotype male: Peru, Yahuarmayo, Inambari River (USMN, holotype not seem; male paratype, NHMUK, examined).
Diagnosis. Sturmiodexia can be differentiated from other genera of Neotropical Dexiini by the following combination of characters: fronto-orbital plate with dense fine hairs, parafacial usually bare, if setulose, just the inferior margin of parafacial presents scattered setulae; facial carina well developed, long plumose arista, prementum 0.5X the head height; posternum and proepisternum bare, thorax with 3 katepisternal setae; wing with cell r4+5 open, without costal spine, bend of vein M angulated; upper calypter hyaline, abdomen ovate, syntergite 1+2 with mid-dorsal longitudinal depression extending to posterior margin, female with one pair of median marginal setae on tergite 3, and male with tergite 3 without marginal seta, both sexes without marginal seta on tergite 1+2, with lateral setae on syntergite 1+2, tergite 4 with a row of marginal setae and tergite 5 with a row of marginal and discal setae.
Distribution. Peru (Puno and San Martin departments); Brazil (Distrito Federal, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Rio de Janeiro and São Paulo states).
Comments. The distinction between the former genus Platyrrhinodexia syn nov. of Sturmiodexia relies mainly on the difference of the ground color of abdomen: it is yellow to tawny yellow in Platyrrhinodexia, while it is reddish yellow to tawny yellow in Sturmiodexia. This character is considered to be very poor and unreliable for supporting a generic distinction between these taxa and supports the hypothesis of the synonymy of Platyrrhinodexia syn nov. with Sturmiodexia. Accordingly, the Neotropical Dexiini now includes 72 genera, and the pernicious effect of the over-splitting made by early authors (e.g., Townsend) is further mitigated as the present work enhances the taxonomic stability of Neotropical tachinid genera. Although only the male terminalia of Sturmiodexia punctulata comb. nov. could be studied, with a description and illustration, the four Neotropical species of Sturmiodexia can be recognized by the straightforward characters given in the species key.
Key to species of Sturmiodexia
- 1Postpedicel tawny orange, but apical ¼ light orange; genal dilatation and inferior margin of parafacial with scattered setulae ……………………………………. 2
- ‒Postpedicel orange; genal dilatation and inferior margin of parafacial bare ……………………………………………………………………………….………. 3
- 2Abdomen with tergite 5 reddish-yellow with golden pruinosity dorsally …………………………………………….. S. moyobambensis (Townsend 1929)
- ‒Abdomen with tergite 5 tawny yellow with silvery pruinosity dorsally …………..………………………………….… S. punctulata (Townsend 1927)
- 3Width of parafacial measured between inner margin of compound eye and antennal insertion is 0.4X the width of gena; abdomen reddish yellow to tawny yellow, with pale golden pruinosity … …………………….S. rubescens Townsend 1919
- ‒Width of parafacial measured between inner margin of compound eye and antennal insertion is 0.8X the width of gena; abdomen yellow to tawny yellow, with silvery pruinosity … ……………………………………S. muscaria (Walker 1853)
Sturmiodexia muscaria (Walker 1853)
(Fig. 1)
Sturmiodexia muscaria (Walker 1853), holotype male (NHMUK). A. Dorsal habitus; B. head, frontal view; C. lateral habitus; D. labels.
Citation: Insect Systematics & Evolution 53, 1 (2022) ; 10.1163/1876312X-bja10022
Dexia muscaria Walker 1853: 308. Type locality: Brazil (without further information).
Ptilodexia muscaria (Walker 1853). Reference: Guimarães (1971: 33 in Ptilodexia, as comb. nov.)
Sturmiodexia muscaria (Walker 1853). Reference: O’Hara et al (2020: 78, list).
Note. There is a label, placed alongside this specimen, by D.M. Wood, dated from 2002, that placed this species in Sturmiodexia.
Type material examined. Holotype ♂: ‘Holo-/type’; ‘Dexia/ Type/ muscaria/ Walk.’; ’68-4’; ‘muscaria’; ‘Brazil./ Ex coll./ Saunders./ 68-4.’; ‘HOLOTYPE ♂/ [not ♀]/ of Dexia/ muscaria Walk/ examined 1970/ R. W. Crosskey.’; ‘NHMUK 013933586’ (NHMUK). Specimen in good condition, but head slightly molded and tergite 3 and 4 damaged on the left side of the dorsal margin.
Redescription of holotype male. Body length: 8.1 mm.
Coloration (Figs. 1A, C): Frontal vitta and ocellar triangle light brown. Fronto-orbital plate silver pruinose, but gena and region of vibrissa light brown. Occiput golden pruinose on upper half, and silvery pruinose on lower half with long and silver to golden setulae. Postpedicel orange. Palpus tawny yellow. Prementum brownish black. Thorax brown to dark brown with silvery to grayish pruinosity; scutum with four dark vittae, in presutural region the two inner vittae are thinner than the outer, in postsutural region, the inner vittae is half the length of the outer, neither reaching the scutellum. Scutellum golden pruinose, but anterior ¼ brownish brown. Wing smoky, slightly light brown along the veins. Calypter hyaline. Halter yellow-tawny, but ¼ proximal brownish black. Posterior spiracle light brown. Legs brownish black. Claw brown, pulvilli yellow. Abdomen yellow to tawny yellow, with silvery pruinose on ¼ to ⅓ in tergites 3 to 5. Syntergyte 1+2 to tergite 4 with a somewhat uninterrupted brownish black vitta on middle. Tergite 5 light yellow with golden pruinose in all tergite. Tergite 3 and 4 with the half of lateral posterior margin brownish black.
Head (Figs. 1B, C): Frontal vitta at its widest point ca. 2.2X as wide as the vertex in dorsal view. Frontal vitta, in the narrowest point, 1.3X the width of ocellar triangle. Inner vertical setae present and outer vertical seta absent. Fronto-orbital plate with 15–16 pairs of proclinate setae; narrower than frontal vitta and parafacial; with setulae along its extension. Postocellar setae proclinate. Width of parafacial measured between inner margin of compound eye and antennal insertion is 0.8X of gena. Postpedicel very slender, 1.3X the combined length of scape and pedicel; arista with ventral cilia longer than the dorsal, longest cilia ca. 7X basal width of arista. Facial carina developed. Facial ridge with six to seven setulae on lower third. Lower facial margin protruding, visible in profile. Vibrissa long, inserted above lower facial margin. Prementum 0.5X as long as head height. Labellum narrow, about 0.3X the prementum.
Thorax (Figs. 1A, C): Acrostichal 2 postsutural setae (the presutural area is damage and is not possible to describe the chaetotaxy). Dorsocentral 2+3. Intra-alar 1+1; intra-postalar absent. Supra-alar 2+2. Postpronotal lobe with five setae. Anepisternum with seven strong setae and with one upward directed setula anteriorly. Scutellum with one basal, one lateral, one apical and two discals pairs of setae. Katepisternum with 3 setae. Anepimerum with one long setae. Notopleuron with 2 equal-sized setae. Postalar callus with 3 setae. Propleuron and prosternum bare. Anatergite bare. Posterior spiracle with posterior lappet larger than anterior. Katepimeron sparsely setulouse.
Wing (Figs. 1A, C): Base of R4+5 dorsally and ventrally setulose. M vein bent forward to R4+5, forming an angle slightly smaller than 90°, and convex after bend. Vein r4+5 with small appendage at bend.
Legs: Fore coxa with many setae anteriorly; fore femur with dorsal and posteroventral rows of setae; fore tibia missing. Mid leg missing. Hind femur with row of anterodrosal and anteroventral setae. Hind tíbia 3 apical third posterodorsal, 1 anterodorsal submedian, 1 anterodorsal and 1 posterodrosal submedian, 4 preapicals, 1 anterodorsal, 1 posterodorsal, 1 posteroventral, 1 anteroventral. Claw straight with the tip curved.
Abdomen (Figs. 1A, C): Syntergite 1+2 with mid-dorsal longitudinal depression extending to posterior margin. Syntergite 1+2 without seta. Tergite 3 with one lateral pair of marginal setae. Tergite 4 with a marginal row of setae. Tergite 5 with two rows of marginal setae.
Terminalia. Not dissected, only male holotype was available.
Female. Unknown.
Biology. Unknown.
Distribution. Brazil.
Sturmiodexia punctulata (Townsend 1927) comb. nov.
Sturmiodexia punctulata (Townsend 1927) comb. nov., paratype male (MZSP). A. Dorsal habitus; B. head, frontal view; C. lateral habitus.
Citation: Insect Systematics & Evolution 53, 1 (2022) ; 10.1163/1876312X-bja10022
Platyrrhinodexia punctulata Townsend 1927: 349. Type locality: Brazil, São Paulo, Itaquaquecetuba.
References. Guimarães (1971: 32, catalogue); Evenhuis et al. (2015: 220, list); O’Hara et al. (2020: 64, checklist of World Tachinidae).
Type material examined. Paratype ♂: ‘Itq[Itaquaquecetuba] 28.I/ Fls. [flowers] Schinus’; ‘dadiva/ Townsend 1926/ 22084’; ‘Platyrrhinodexia punctulata TT ♂/ DetCHTT Paratype’; ‘PARATIPO’ (MZSP).
Adicional material examined: BRAZIL: Distrito Federal: Brasilia, Guaratiba, 2 ♂ 6.viii.1961, J.H. Guimarães col. (MZSP); Mato Grosso: Poconé, Fazenda Rio Clarinho, Margem oposta do Rio Claro, S16º36’ 24,8” W 56º 43’ 16,7”, 1 ♀, 17.vii–16.viii.2012, Lamas, Nihei & eq. col. [SISBIOTA CNPq/Fapesp] (MZSP); Mato Grosso do Sul: Bodoquena, Fazenda Califórnia – topo, S20º 41’ 55,9” W56º 52’ 49,4”, 2 ♂, 21.iii – 06.iv.2012, Lamas, Nihei & eq. col. [SISBIOTA CNPq/Fapesp] (MZSP); Minas Gerais: Pedra Azul, 1 ♂, xi-72, Seabra & Oliveira col. (MNRJ); Rio de Janeiro: Rio de Janeiro, Jardim Botânico, 1 ♂, 7.1936, H.S. Lopes col. (MNRJ); Rio de Janeiro, Itajai, 1 ♂, ix. 1948, M[essias]. Carrera col. (MZSP); Rio de Janeiro, Macaé, Restinga da Barra de Macaé, S22º 57’41,4” w 42º51’20,3”, 1 ♂ (dissected), 14 e 15.ii.2011, Nihei & eq. col. (MZSP); Rio de Janeiro, 1 ♀ (dissected), 1932, R.H. Manguinhos col. (MZSP).
Redescription of paratype male. Body length: 7.6 mm.
Coloration (Figs. 2A, C): Frontal vitta and ocellar triangle light brown. Fronto-orbital plate silver pruinose, but gena and region of vibrissa light brown. Occiput golden pruinose on upper half, and silvery pruinose on lower half with long and silver to golden setulae. Postpedicel orange. Palpus tawny yellow. Prementum brownish black. Thorax brown to dark brown with silvery to grayish pruinosity; scutum with four dark vittae, in presutural region the two inner vittae are thinner than the outer, in postsutural region, the inner vittae is half the length of the outer, neither reaching the scutellum. Scutellum golden pruinose, but anterior ¼ brownish brown. Wing smoky, slightly light brown along the veins. Calypter hyaline. Halter yellow-tawny, but ¼ proximal brownish black. Posterior spiracle light brown. Legs brownish black. Claw brown, pulvilli yellow. Abdomen yellow to tawny yellow, with silvery pruinose on ¼ to ⅓ in tergites 3 to 5. Syntergyte 1+2 to tergite 4 with a somewhat uninterrupted brownish black vitta on middle. Tergite 5 light yellow, silvery pruinose in all tergite. Tergite 3 and 4 with the half of lateral posterior margin brownish black.
Head (Figs. 1B–C): Frontal vitta at its widest point ca. 2.2X as wide as the vertex in dorsal view. Frontal vitta, in the narrowest point, 1.3X the width of ocellar triangle. Inner vertical setae present and outer vertical seta absent. Fronto-orbital plate with 15–16 pairs of proclinate setae; narrower than frontal vitta and parafacial; with setulae along its extension. Postocellar setae proclinate. Width of parafacial measured between inner margin of compound eye and antennal insertion is 0.8X of gena. Postpedicel very slender, 1.3X the combined length of scape and pedicel; arista with ventral cilia longer than the dorsal, longest cilia ca. 7X basal width of arista. Facial carina developed. Facial ridge with six to seven setulae on lower third. Lower facial margin protruding, visible in profile. Vibrissa long, inserted above lower facial margin. Prementum 0.5X as long as head height. Labellum narrow, about 0.3X the prementum.
Thorax (Figs. 2A, C): Acrostichal 2+2. Dorsocentral 2+3. Intra-alar 1+1; intra-postalar absent. Supra-alar 2+2. Postpronotal lobe with five setae. Anepisternum with seven strong setae and with one upward directed setula anteriorly. Scutellum with one basal, one lateral, one apical and two discal pairs of setae. Katepisternum with 3 setae. Anepimerum with one long setae. Notopleuron with 2 equal-sized setae. Postalar callus with 3 setae. Propleuron and prosternum bare. Anatergite bare. Posterior spiracle with posterior lappet larger than anterior. Katepimeron sparsely setulouse.
Wing (Figs. 2A, C): Base of R4+5 dorsally and ventrally setulose. M vein bent forward to R4+5, forming an angle slightly smaller than 90°, and convex after bend. Vein r4+5 with small appendage at bend.
Legs: Fore coxa with many setae anteriorly; fore femur with dorsal and posteroventral rows of setae; fore tibia missing. Mid femur with a row of anteroventral seta; three posteroventral on apical third. Mid tibia two anterodorsal seta on median third, and 2 anteroventral seta on submedian, 1 posterior on submedian, 6 preapicals, 2 anterodorsals, 1 anterior and 1 ventral, 1 posteroventral and 1 anteroventral. Hind femur with row of anterodorsal and anteroventral setae. Hind tibia 3 apical third posterodorsal, 1 anterodorsal submedian, 1 anterodorsal and 1 posterodorsal submedian, 4 preapicals, 1 anterodorsal, 1 posterodorsal, 1 posteroventral, 1 anteroventral. Claw straight with the tip curved.
Abdomen (Figs. 2A, C): Syntergite 1+2 with mid-dorsal longitudinal depression extending to posterior margin. Syntergite 1+2 without seta. Tergite 3 with one lateral pair of marginal setae. Tergite 4 with a marginal row of setae. Tergite 5 with two rows of marginal setae.
Male terminalia (Fig. 3): Tergite 6 undivided, about ⅒ the length of syntergosternite 7+8. Syntergosternite 7+8 broad. Sternite 6 asymmetric. Sternite 5 with weal developed lobules, setulose. Ejaculatory apodeme small, approximately equal size in length in relation to surstylus, with anterior region very narrow and enlarging posteriorly. Epandrium broad in posterior view, setulose, and closed dorsally. Anterior epandrial process well developed. Hypandrial arm long, hypandrial apodeme clearly distinguishable, with central plate narrow. Cerci not fused, broad basally, and distally tapered in posterior view, narrow basally, in lateral view. Surstylus broad, not fused with epandrium, convex, and setulose; distally tapered in posterior view. Bacilliform sclerite rod-like. Epiphallus present, fused with basiphallus. Pregonite and postgonite fused as curved elongate structure, with a distinct separation; pregonite connected basally to the hypandrium by sclerotized seam. Basiphallus bifurcated in posterior view, as long as postgonite. Distiphallus with extension of dorsal sclerite long; dorsal sclerite ventrally serrulate; granular zone present, longer that the half of the dorsal sclerite.
Sturmiodexia punctulata (Townsend 1927) comb. nov., Rio de Janeiro, Brazil (MZSP). Male terminalia. A. Syntergosternite 7+8; B. Sternite 5; C. epandrium, cerci and surstylus, lateral view; D. epandrium, cerci and surstylus, posterior view; E. hypandrium, phallapodeme, basiphallus, epiphallus, distiphallus, pregonite and postgonite, lateral view. Abbreviations: basph = basiphallus; distph = distiphallus; epiph = epiphallus; hypd = hypandrium; pgt = postgonite; phapod = phallapodeme; pregt = pregonite.
Citation: Insect Systematics & Evolution 53, 1 (2022) ; 10.1163/1876312X-bja10022
Female. Differs from male by the following: two strong proclinate and one reclinate fronto-orbital setae. Fronto-orbital plate as wide as both frontal vitta and parafacial. Abdomen ovate in dorsal view, not as elongate as in males. Tergite 3 with one pair of marginal setae. Claw and pulvilli shorter than tarsomere 5.
Female terminalia (Fig. 4C): Tergite 6 and 7 complete dorsally, with setae in all tergite 6 and with few setae on the posterior margin of tergite 7. Tergite 8 absent. Sternite 6 and 7 complete ventrally, with few setae in all posterior margin. Sternite 8 subrectangular with setulae in the entire surface. Sternite 10, as a narrow strip, with setula only on the posterior margin. Cerci well developed, sub-circular, with several setae apically with sternite 9. Syntergite 9+10 absent. Three spermatheca; equal sized; oval with apical portion with a pore and surface entirely rugose.
Sturmiodexia punctulata (Townsend 1927) comb. nov., Rio de Janeiro, Brazil (MZSP). A. first instar larva; B. cephaloskeleton; C. female terminalia. Abbreviations: AS = accessory sclerite; ant = antenna; C = cercus; DC = dorsal cornua; IR = intermediate region; MD = mouth hook; polyg plat = polygonal platelets; post spir = posterior spiracle; SG = sclerite of salivary gland; S6 = sternite 6; S7 = sternite 7; S8 = sternite 8; S10 = sternite 10; T6 = tergite 6; T7 = tergite 7; VC = ventral cornua.
Citation: Insect Systematics & Evolution 53, 1 (2022) ; 10.1163/1876312X-bja10022
First instar larvae (Figs. 4A–B): First segment with an elongate antenna, recurved clavate cephalic sensorium well developed. Cephaloskeleton thin and lightly sclerotized, with nearly straight mouth hook; intermediate region indistinct; dorsal and ventral cornua slightly diverging from each other; accessory sclerite posteriorly broad, narrowing anteriorly, anterior to mouth hook; sclerite of salivary gland as strip. Body covered with polygonal platelets; those covering segments 2–12 bearing a few spines on hind margin; segment 1 with small spines distributed uniformly; 12 on posterior margin with rows of spines posteriorly directed; with a pair of spines on middorsal surface. Posterior spiracles on small posterior protuberances in segment 12.
Biology. Unknown.
Distribution. Brazil (Distrito Federal, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Rio de Janeiro and São Paulo states).
Note. New records from Brazil: Distrito Federal, Mato Grosso, Mato Grosso do Sul, Minas Gerais and Rio de Janeiro states.
Sturmiodexia rubescens Townsend 1919
(Fig. 5)
Sturmiodexia rubescens Townsend 1919, paratype male (NHMUK). A. Dorsal habitus; B. head, frontal view; C. lateral habitus.
Citation: Insect Systematics & Evolution 53, 1 (2022) ; 10.1163/1876312X-bja10022
Sturmiodexia rubescens Townsend 1919: 550. Type locality: Peru, Yahuarmayo.
References. Guimarães (1971: 35, catalogue); Evenhuis et al. (2015: 255, list); O’Hara et al. (2020: 78, checklist of World Tachinidae).
Type material examined. Paratype ♂: ‘Syn-/type’; ‘Sturmiodexia/ rubescens / Tns’; ‘Yahuarmayo/ 9. II.10/ Peru’; ‘CHTTownsend/ col’; ParatypeNo./ 22233/ U.S.N.M.’; ‘In exchange with/ Prof. J. M. Aldrich./ Brit. Mus. 1929-366.’; ‘NHMUK 013933562’ (NHMUK).
Redescription of paratype male. Body length: 7.6 mm.
Coloration (Figs. 5A, C): Frontal vitta light brown and ocellar triangle brownish black. Fronto-orbital plate pale golden pruinose, but gena brownish black. Occiput golden pruinose on upper half, and silvery pruinose on lower half with long and silver to golden setulae. Postpedicel orange. Palpus tawny yellow. Prementum brownish black. Thorax brown to dark brown with whitish to grayish pruinosity; scutum with four dark vittae, in presutural region the two inner vittae are thinner than the outer, in postsutural region, the inner vittae is half the length of the outer, neither reaching the scutellum. Scutellum golden pruinose, but anterior ¼ brownish brown. Wing smoky, slightly light brown along the veins. Calypter hyaline. Halter with knob light yellowy, steam yellow-tawny, but ¼ proximal brownish black. Posterior spiracle brownish black. Legs brownish black. Claw brown, pulvilli yellow. Abdomen yellow to tawny yellow, with whitish pruinosity in all, easily seen on posterior view. Syntergyte 1+2 to tergite 5 with a somewhat brownish black vitta on middle. Tergite 3 and 4 with about the half of lateral posterior margin brownish black.
Head (Figs. 5B–C): Frontal vitta at its widest point ca. 2.2X as wide as the vertex in dorsal view. Frontal vitta, in the narrowest point, 1.2X the width of ocellar triangle. Inner vertical setae present and outer vertical seta absent. Fronto-orbital plate with 14–15 pairs of proclinate setae; narrower than frontal vitta and parafacial; with setulae along its extension. Postocellar setae proclinate. Width of parafacial measured between inner margin of compound eye and antennal insertion is 0.5X of gena. Postpedicel very slender, 1.5X the combined length of scape and pedicel; arista with ventral cilia longer than the dorsal, longest cilia ca. 7X basal width of arista. Facial carina developed. Facial ridge with 9 to 10 setulae on lower third. Lower facial margin protruding, visible in profile. Vibrissa long, inserted above lower facial margin. Prementum 0.5X as long as head height. Labellum narrow, about 0.3X the prementum.
Thorax (Figs. 5A, C): Acrostichals 2+2. Dorsocentral 3+3. Intra-alar 2+1; intra-postalar present. Supra-alar 2+3. Postpronotal lobe with five setae. Anepisternum with eight strong setae and with one upward directed setula anteriorly. Scutellum with two basals, one lateral, one apical and two discals pairs of setae. Katepisternum with 3 setae. Anepimerum with one long setae. Notopleuron with 2 equal-sized setae. Postalar callus with 3 setae. Propleuron and prosternum bare. Anatergite bare. Posterior spiracle with posterior lappet larger than anterior. Katepimeron sparsely setulouse.
Wing (Figs. 5A, C): Base of R4+5 dorsally and ventrally setulose. M vein bent forward to R4+5, forming an angle slightly smaller than 90°, and convex after bend. Vein r4+5 with small appendage at bend.
Legs: Fore coxa with many setae anteriorly; fore femur with dorsal and posteroventral rows of setae; fore tibia with 2 anterodorsal setae on submedian, 4 preapicals, 1 anterior, 1 anterodorsal and 1 posterior, 1 posteroventral. Mid femur with a row of anteroventral seta; three posteroventral on apical third. Mid tibia with two anterodorsal seta on median third, and 2 anteroventral seta on submedian, 1 posterior on submedian, 6 preapicals, 2 anterodorsals, 1 anterior and 1 ventral, 1 posteroventral and 1 anteroventral. Hind femur with row of anterodrosal and anteroventral setae. Hind tibia 3 anterodorsal and 3 posterodrosal submedian, 2 anteroventral on distal third, 4 preapicals, 1 anterodorsal, 1 posterodorsal, 1 posteroventral, 1 anteroventral. Claw straight with the tip curved.
Abdomen (Figs. 5A, C): Syntergite 1+2 with mid-dorsal longitudinal depression extending to posterior margin. Syntergite 1+2 and Tergite 3 with one pair of lateral setae. Tergite 3 with one pair of lateral setae. Tergite 4 with a marginal row of setae. Tergite 5 with two rows of marginal setae.
Terminalia. Not dissected, only male paratype was available.
Biology. Unknown.
Distribution. Peru.
Discussion
The circumscription of Dexiini is characterized by traits from the male terminalia and from the first instar larva. Cerretti et al. (2014), in the first morphological phylogenetic analysis for Tachinidae, recovered two synapomorphies for Dexiini: male terminalia with broad and massive surstylus and distiphallus with acrophallus as a granular structure. Both of these derived traits can be found in Sturmiodexia, confirming its placement in Dexiini. Furthermore, the presence of small and irregular plates on cuticle of the first instar larva, a traditional putative synapomorphy for Dexiini (Thompson 1963), further confirms the placement of this genus within this tribe. However, at the moment, it is not possible to discuss the placement of the Neotropical Sturmiodexia within Dexiini without a broader phylogenetic study involving a considerable amount of sample of Dexiini taxa, mainly from the Neotropical region. Even if Sturmiodexia can be diagnosed promptly from other genera of Neotropical Dexiini (as given in the diagnosis above), no putative synapomorphy could be stated from all the species of this genus. Still, the presence of rows of spines posteriorly directed, in addition to the pair of spines on middorsal surface the segment 12 of the first instar larva in S. punctulata, can be a putative synapomorphy for Sturmiodexia, as it is absent in other allied genera like Billaea Robineau-Desvoidy, 1830 (Thompson 1960), Prophorostoma Townsend, 1927, Prosenoides Brauer & Bergenstamm, 1891 (Thompson 1963) and Rhamphinina Bigot, 1885 (Thompson 1963). The overall lack of data from the first instar larva in Sturmiodexia (only present for S. punctulata), that could confirm if this genus is monophyletic, is a common trend in Dexiini and in the whole family. Yet, by presenting the first description and illustration of a first instar larva of this genus, this work makes a contribution to overcome this trend of lack of data that still happens currently. Without this data, a whole set of traits may remain hidden when the immature stages, that are known to present some remarkable traits in tachinids (e.g., Thompson 1963; Richter & Farinets 1983), are not properly investigated.
Acknowledgments
I would like to thank the Institute of Biosciences of the University of São Paulo and Silvio Nihei (USP) for the logistical support. I am indebted to Nigel Wyatt (NHMUK) for facilities and kind assistance during my visit, and for kindly allowing me to use the image capturing system of the NHMUK for taking photographs. Thanks to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (process number 88882.333078/2019-01) for doctoral scholarship.
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