Heterostomus curvipalpis Bigot, 1857

Coscarón, Sixto, Coscarón, María Del Carmen & Gil-Azevedo, Leonardo H., 2013, On the enigmatic Heterostomus curvipalpis Bigot, 1857, with a description of the pupa (Diptera, Brachycera), Zootaxa 3616 (3), pp. 268-276 : 269

Heterostomus curvipalpis Bigot, 1857

( Figs. 1–23 )

Heterostomus curvipalpis Bigot, 1857: 285 ; Malloch, 1932: 204; Nagatomi, 1984:115; 1985: 699.

Adult ( Figs. 1–14 ): Large species, wing length 13.0–18.0 mm, eyes bare; face with upper and mid lower part scarcely produced anteriorly; conspicuous ocelli; antennal flagellum with eight flagellomeres, palpus with two flattened articles, proboscis fleshy and surpassing palpus length ( Figs. 1 , 5 , 12, 14 ); male holoptic. Scutum flat ( Figs. 9, 10 ); postmesonotum and postscutellum present; metathorax with postspiracular plate. Wing elongate ( Figs. 8 , 13 ), vein C reaching wing apex, vein R1 setose, R2+3 anteriorly curved from medial portion and ending very close to R1 apex; basal radial cell elongate, its apex surpassing the middle of discal cell; R4 arising from anterior third of R5, which ends just at the wing apex; M1 ending posterior to the wing apex, vein M3 curved but not fusing with Cu–A1, thus cell m3 open at wing margin, CuA1 arises from the apex of basal medial cell, posterior cubital cell closed; alula scarcely developed and lower calypter well developed, with a tuft of long pubescence. Tibial spurs 1:2:2. Abdomen elongate and flattened, gradually narrowed beyond VII segment ( Fig. 11 ).

Female genitalia: tergite IX membranous at middle, tergite X divided; cerci with two segments ( Fig. 2 ), with a few developed subapical sensorial pits on internal side; genital fork wide basally, with thick spermathecal ducts at base ( Fig. 4 ).

Male genitalia ( Fig. 6 ): gonocoxites fused dorsally, gonostylus subtriangular, short and externally curved; parameral sheath surrounding the aedeagus; tip of the aedeagus well developed; ejaculatory apodeme extended posteriorly by endoaedeagal guide, lateral aedeagal apodeme large; spermatic pump subcylindric and enlarged; gonocoxal apodemes relatively thick and greatly projected anteriorly. Tergites IX and X fused ( Fig.7 ) (= epandrium), cerci subquadrangular; sternite IX expanded (= hypoproct).

Pupa (female, emerged in the laboratory) ( Figs. 15–23 ): Exuvial coloration reddish brown, uniformly glossy, slightly darker on thoracic and abdominal spiracles, and with blackish spines forming abdominal rings on each segment. Length 30.0 mm.

Frontal and cephalic sclerites unknown (lost during the emergence). Thorax dorsally with transverse sulcus ( Fig. 16, 17 ) on anterior 3/4 and small lateral rugosities (wrinkled areas). Mesothoracic spiracle prominences slightly elevated (0.8 mm) ( Figs. 16, 17, 18, 19 ). Spiracle slit placed transversely on the apex of the prominence, is arched and elongated, showing curved like a semicircle on both extremes and without projection. Wing and leg sheaths of equal length, extended surpassing a little the first abdominal segment border. Mesonotum with three separated spines on each side: one anterolateral, one mediodorsal and one submediandorsal. Abdominal spines appear seta-like,stout at base and thinly prolonged distally. First abdominal tergum with 9+9 stout spines approximately equidistant, five of them more dorsal in position; the following four spines on pleura are closer to each other. Subsequent abdominal segments II–VII with two uniseriate and continuous rows of spines and without setae, and delimiting, in combination with the intersegmental sutures, three annular stripes, all around each segment and of approximately same length ( Figs. 15, 16, 20, 21 ). Middle stripes between spine rings smoother and glossier. First rows of spines smaller than the second, and absent ventrally between the respiratory spiracles area. The second rows of spines are complete around the ring segment; the spines are longer dorsally and in the VII segment some grouped forming a spur ( Fig. 22 ). Segments II –VII with the first rows of spines with 46, 52, 50, 62, 50, 38 spines per segment, respectively; and the second rows of spine with 86, 96, 106, 94, 64, 50 spines per segment, respectively. Anal segment without spines, but with small rugose anterior stripe-like area in the preceding apical segments. VIII segment with eight large wrinkled and well sclerotized tubercles, forming the aster, arranged as following: 1+1 dorsal (1.2 mm), 2+2 lateral (1.1 mm), and ventral (0.7 mm); dorsally there is a comb of 11–12 small spines ( Fig. 23 ), and internally on base of lateral spines, there are another two small acuminate tubercles ( Figs. 22, 23 ). Seven subconical abdominal respiratory spiracles with similar shape (0.36 mm) ( Fig. 15 ), and positioned lateroanteriorly on segments I–VII ( Figs. 15–16 ).

Figures

FIGURES 1 – 4. Heterostomus female. 1: head, frontal view. 2: terminal abdominal segments (epigynium), shown on left side the ventral view, and on right side dorsal view. ce: cerci, hy: hypoproct, TIX and X: ninth and tenth tergites. 3: distal portion of hypogynium (eighth sternite and gonapophysis). 4: genital fork with basal parts of spermathecal ducts.

FIGURES 5 – 8. Heterostomus male. 5: head, lateral view. 6: hypopygium, shown on left side the ventral view, and on right side dorsal view. gs: gonostyle, gx: gonocoxite, aa: aedeagal apodeme, pa: parameral sheath, at: aedeagus tip, ea: ejaculatory apodeme, eg: endoaedeagal guide, eh: endophalic hilt, ea: ejaculatory apodeme, gap: gonocoxal apodeme, la: lateral apodeme, sp: sperm pump. 7: epandrium (ep) (tergites IX and X fused), shown on left side the ventral view, and on right side dorsal view. hy: hypoproct. 8: wing.

FIGURES 9 – 14. Heterostomus female. 9: lateral view. 10 – 13: dorsal view. 14: frontal view.

FIGURES 15 – 23. Heterostomus pupa. 15, 18, 19, 22: lateral view. 16, 17, 20, 21: dorsal view. 23: aster in posterior view. 17 and 19: arrows points spiracle.