Stegana (Steganina) schildi Malloch, 1924

Bächli, Gerhard & Vilela, Carlos R., 2022, On the identities of Neotropical Stegana species (Diptera, Drosophilidae). III. Four Costa Rican species described by J. R. Malloch, Revista Brasileira de Entomologia (e 20210113) 66 (1), pp. 1-23 : 12-17

Stegana (Steganina) schildi Malloch, 1924

( Figs. 17–25 )

Stegana schildi Malloch, 1924a: 99 (key, description); Malloch, 1924b: 5 (description); Heed, 1956: 3 (distribution); Heed, 1957: 76 (distribution); Wheeler, 1970: 79.7 (affiliation).

Stegana (Steganina) schildi Malloch : Wheeler, 1960:110 (affiliation); Wheeler, 1981: 31 (affiliation); Brake and Bächli, 2008: 299 (affiliation).

Type locality: Costa Rica, Province of Alajuela, Canton of San Mateo, Higuito.

Diagnosis.Generally blackish flies.Front yellowish, with a conspicuous shining black, slightly prominent transverse stripe in the lower third. Pleura pale with an upper, distinct black band and a lower brownish band. Surstylus linked to the epandrium by membranous tissue,double-walled, outer wall not microtrichose, scarcely setose in the lower region, inner wall brush-like, with ca.40 strong, curved,sharp-tipped setae; prensisetae reduced to two, blunt and widely spaced apart pegs.Hypandrium strongly sclerotized,anterior margin deeply concave, laterally projected anterad by narrow sclerotized lamellae, posterior margin slightly concave;posterior hypandrial process absent; dorsal arch strongly sclerotized; gonopods fused to each other and posterior margin of hypandrium, devoid of seta. Aedeagus spatulate, 1/2 length of aedeagal apodeme with which it is fused. Aedeagal apodeme rod-shaped, laterally sinuate in the dorsal and ventral views.Ventral rod tongue-shaped,strongly sclerotized,linked to the posterior margin of the hypandrium and outer paraphysis by membranous tissue. Outer paraphysis reduced, bearing one large and two tiny setulae, linked to the supposedly fused gonopods (posterior hypandrial margin) and the apicolateral margin of the ventral rod.

Material examined (n = 9)

Holotype ♀ [#21, dissected] labeled ( Fig. 17 ): “ Higuito / SanMateoCR [ Costa Rica] / PabloSchild / coll // Stegana / schildi / Type [handwritten] / Det./ J R Malloch [printed] // Type No./ 26674 [handwritten] / U.S.N.M. [red label] // USNMENT / [QR Code] / 01097758 [back side] // Stegana / schildi Malloch / Bächli & Vilela det. 2017 // HOLOTYPE [red label] // ♀” . Paratypes ♀♀ [#13–18; dissected: #13, #16, #17)]: same data as holotype, except Type and QR code labels. Non-type specimen ♂ [#20, dissected] labeled: “ Cano Saddle [apparently a dike] / Gatun L. [Lake (artificial, huge), part of Panama Canal Zone formed by the Gatun Dam in Chagres river], Pan [Panama] / RCShannon / V.13.1923 [handwritten] // Stegana / schildi Mall. [handwritten] / Det / J R Malloch // USNMENT [QR Code] / 01372797 [back side] // Stegana / schildi Malloch / Bächli & Vilela det. 2017 // ♂ ” ; ♀ [#19] labeled: “ COSTA RICA / La Suiza [de Turrialba] / April 1922 / Pab.[Pablo] Schild coll.// ALMelander / Collection / 1961 [green right half] // Stegana / schildi / Mall [handwritten] // USNMENT [QR code] 01372796 [back side] // ♀” .

Comments. Malloch (1924b) listed one male type [holotype], one allotype [female] and five paratypes. However, the type specimen series we have received contains seven female specimens (1 ♀ labeled type [holotype] plus 6 ♀♀ labeled paratype).

Redescription

♂. (n = 1). Head. Frons ( Fig. 22 ) glossy, yellowish with a more or less darkened spot around the ocellar triangle, with a conspicuous shining black, slightly prominent transverse stripe in the lower third, the upper margin medially narrowed. Frontal length 0.61 mm; frontal index about 1.33, top to bottom width ratio about 1.22, frontal triangle hardly visible, about 40% of the frontal length; ocellar triangle black, prominent, about 25% of the frontal length. Orbital plates about 60–65% of the frontal length. Orbital setae almost arranged in a line, distance of or3 to or2 about 57% of or3 to or1, distance of or2 to or1 about 43% of or3 to or1, distance of or3 to or1 about 200% of or3 to vtm, vt index about 0.83, ocellar setae about 50% of frontal length; vibrissal index about 0.32. Face black in about upper half, white below. Carina narrow, prominent in the upper half of the face. Cheek white, broad, index about 6. Eye oblong, main axis distinctly oblique, index about 1.38. Occiput black in upper 5/6, white below. Pedicel yellowish. Flagellomere 1 slightly narrowed apically, black, with a narrow yellowish base and a length-to-width ratio of about 2.22. Arista with 10 dorsal, 7 ventral and about 7 rather long inner branches, plus a short terminal fork. Proboscis and palpus yellowish.

Thorax length about 2.28 mm. Scutum ( Fig. 21 ) predominantly slightly microtrichose, brownish, paler on the frontal margin, with a paler median and a lateral stripe outside the dc lines, each preceded by a small somewhat circular pale spot; about 8 rows of acrostichal setae. One postpronotal seta: dc index about 0.39. Scutellum somewhat longish, apically slightly pointed, with a pale median stripe, scutellar setae nearly equidistant, lateral ones diverging, apical ones crossed, scut index about 1.85.Pleura ( Fig.21a, b ) yellowish, with a broad, black stripe in upper third and a diffuse dark stripe or spot in the upper half of the katepisternum, sterno index about 0.86. Haltere with a yellow knob. Legs ( Fig. 21a,b,d ) generally yellowish; fe1 with a dorso-apical dark spot, midleg brownish, with fe2 basally and apically yellowish and ti2 yellowish in the apical fourth, hindleg as midleg, but paler; preapical and ventral apical setae on ti2.

Wing ( Fig. 21c,d ) apically pointed, generally dark brown, paler along the hind margin, costa apically with 9–11 warts below, r 2+3 apically bent towards the costa, both crossveins with a small shadow, m 3 somewhat sigmoid, length 3.29 mm, length to width ratio about 2.09. Indices: C = 1.93, hb = 0.85, 4C = 1.29, 4v = 1.81, 5x = 1.00, M = 0.48, prox. x = 1.05.

Abdomen ( Fig. 21d ) glossy, dark brown, tergites with a diffuse blackish hind margin.

Terminalia ( Figs. 23-25 ). Epandrium microtrichose and setose, except for the anterior region and ventral lobe, with ca. 20 upper and no lower setae; ventral lobe ( Fig. 23a ) bare, projected inwards, mostly covering the surstylus.Cercus reduced to a narrow vertical stripe, setose, not microtrichose, without a ventral lobe and anteriorly linked to the epandrium by membranous tissue. Surstylus basally narrow, distally wide, curved inwards, ventromarginally bearing a row of small curved setae, double-walled, outer wall not microtrichose, scarcely setose in the lower region, inner wall like a brush, densely covered in the posteromedial area with ca. 40 strong, curved, sharply-tipped setae, probably supporting the function of prensisetae, which are scarce (just two, widely separated, upper one sharp, lower one blunt; Fig. 23c ) on the inner margin of the surstylus, base of surstylus linked to the epandrium by membranous tissue. Decasternum medianly projected posterad, distolaterally bifid, distoventrally fused to the surstylus’ inner wall. Hypandrium strongly sclerotized, slightly wider than long and shorter than the epandrium, anterior margin deeply concave, laterally projected anterad like two somewhat squared table legs, lateral margin sinuate in the lateral view, bench-shaped in the anterior and posterior views, posterior margin slightly concave; posterior hypandrial process absent; dorsal arch strongly sclerotized, V-shaped and sinuate in the dorsal view, perpendicular and laterally fused to the hypandrium arms, dorsodistally slightly projected forwards and marginally serrate in the lateral view; gonopods fused to each other and to posterior margin of the hypandrium, devoid of seta. Aedeagus ( Figs. 24 , 25 ) dorsoventrally flattened, spatulate, bare, ca. 1/2 length of the aedeagal apodeme, and fused to each other. Aedeagal apodeme, curved, rod-shaped, anteriorly expanded dorsoventrally, twice as long as the aedeagus. Ventral rod strongly sclerotized, tongue-shaped, anteroposteriorly flattened, curved in the lateral view, linked to the posterior margin of the hypandrium and outer paraphysis by membranous tissue. Outer paraphysis reduced, bearing one large and two tiny setulae, linked to the supposedly fused gonopods (posterior hypandrial margin) and apicolateral margin of the ventral rod. Ejaculatory apodeme ( Fig. 24e,f ) strongly sclerotized and somewhat similar to the aedeagus in the lateral view ( Fig.24e ), plate ca. 43% of the handle length, and handle ca. 67% of the aedeagus+aedeagal apodeme length ( Fig. 24a ), the inner angle between the handle and plate> 90°; plate trapezoid-shaped in the posterior view ( Fig. 24f ).

♀. (n = 8). Differences compared to males: No obvious differences in external morphology (Figs, 18, 19). Measurements: Frontal length about 0.54 (0.47–0.65) mm. Frontal index about 1.27 (1.19–1.46), top to bottom width ratio about 1.20 (1.16–1.27), or1 / or3 ratio about 0.98 (0.85–1.14), or2 / or1 ratio about 0.71 (0.61–0.76), postocellar setae about 28 (21–34) % of the frontal length, ocellar setae about 44 (41–53) % of the frontal length, vt index about 0.92 (0.78–1.00), vibrissal index about 0.32 (0.28–0.35). Cheek index about 5 (4–7). Eye index about 1.32 (1.24–1.41). Flagellomere 1 ratio about 1.91 (1.60–2.14).

Thorax length about 1.86 (1.56–2.04) mm, dc index about 0.42 (0.39–0.46), scut index about 1.66 (1.08–2.06), sterno index about 0.86 (0.71–0.95).

Wing length 2.80 (2.38–3.22) mm, length to width ratio about 1.95 (1.79–2.09). Indices: C = 1.91 (1.78–2.04), hb = 0.81 (0.74–0.88), 4C = 1.23 (1.10–1.33), 4v = 1.74 (1.62–1.89), 5x = 0.94 (0.89–1.00), M = 0.46 (0.42–0.50), prox. X = 0.98 (0.88–1.17).

Terminalia (n = 1) ( Fig. 20 ). One pair of finger-shaped cerci inserted beyond and between the epiproct and hypoproct. Oviscapt valves absent, sternite 8 (egg guide of Laštovka and Máca, 1982) horizontally positioned, somewhat trapezoid-shaped, with a straight posterior margin not protruding beyond the hypoproct. It does not bear peg-shaped ovisensilla, and its size and trichoid ovisensilla are similar to the setae of the preceding rectangle-shaped sternites. Inner spermathecal capsule bulbous, with a tailed appendage ( Laštovka and Máca, 1982) as long as sternite 8.

Distribution. Costa Rica (Provinces of Alajuela and Cartago), Panama (Canal Zone) [new record].

Biology. Unknown.

Figures

Figure 17 Stegana schildi Malloch, 1924, labels of female holotype #21.

Figure 18 Stegana schildi Malloch, 1924, female holotype #21, Higuito,San Mateo, Alajuela, Costa Rica [Type Number 26674, USNM], habitus, four views:a, oblique dorsal, b, left lateral, c, head, thorax and wings dorsal, d, abdomen dorsal. Scale bar = 1 mm.

Figure 19 Stegana schildi Malloch, 1924, female holotype #21, Higuito,San Mateo, Alajuela, Costa Rica [Type Number 26674, USNM],habitus, two close-up views: a, head dorsal, b, tip of left wing ventral [optically cut anteroventrally].Scale bar = 1 mm.

Figure 20 Stegana schildi Malloch, 1924, female holotype #21, Higuito, San Mateo, Alajuela, Costa Rica [Type Number 26674, USNM], distal abdomen, ventral [ventral receptacle partially extruded]. Scale bar = 1 mm.

Figure 21 Stegana schildi Malloch,1924,non-type male #20, Cano Saddle,Gatun L., Panama,[13.V.1923, R.C.Shannon coll.,J.R.Malloch det., USNM],habitus,four views:a,oblique dorsal, b, right lateral, c, thorax dorsal, d, abdomen dorsal.Scale bar = 1 mm.

Figure 22 Stegana schildi Malloch, 1924, non-type male #20, Cano Saddle, Gatun L., Panama, [13.V.1923, R.C.Shannon coll., J.R.Malloch det., USNM], habitus, two close-up views: a, head left lateral, b, head dorsal. Scale bar = 1 mm.

Figure 23 Stegana schildi Malloch, 1924, non-type male #20, Cano Saddle, Gatun L., Panama, [13.V.1923, R.C. Shannon coll., J.R. Malloch det., USNM], external terminalia, four views: a, epandrium, surstylus, and cercus, left lateral, b, epandrium, surstyli, and cerci, oblique posterior, c, idem, ventroposterior, d, idem, posterior.Scale bar = 0.1 mm.

Figure 24 Stegana schildi Malloch, 1924, non-type male #20, Cano Saddle, Gatun L., Panama, [13.V.1923, R.C. Shannon coll., J.R. Malloch det., USNM], inner terminalia, several views: a, hypandrium+gonopod, aedeagus+aedeagal apodeme, ventral rod, and left outer paraphysis, left lateral, b, idem, oblique anterior, c, idem, plus right paraphysis, oblique posterior, d, hypandrium+gonopods, and aedeagus+aedeagal apodeme, dorsal, e, ejaculatory apodeme left lateral, f, idem, posterior.Scale bar = 0.1 mm.

Figure 25 Stegana schildi Malloch, 1924, non-type male #20, Cano Saddle, Gatun L., Panama, [13.V.1923, R.C. Shannon coll., J.R. Malloch det., USNM], five views of the aedeagus+aedeagal apodeme, ventral rod, and outer paraphyses, from dorsal through ventral. Scale bar = 0.1 mm.