Hirtodrosophila orbospiracula (Patterson and Wheeler)

Grimaldi, David A., 2018, Hirtodrosophila Of North America (Diptera: Drosophilidae), Bulletin of the American Museum of Natural History 2018 (421), pp. 1-1 : 1-

Hirtodrosophila orbospiracula (Patterson and Wheeler)

Figures 9 , 16B , 29

Drosophila (Hirtodrosophila) orbospiracula Patterson and Wheeler, 1942: 70 .

DIAGNOSIS: Known only from male. Like H. chagrinensis tergites 1–5 each with completely transverse dark posterior bands; distinctive among all North American species for the light head and body (even the basal flagellomere and palp) and yellowish wing; acrostichals in front of anterior dorsocentral enlarged, carina relatively well developed. Male: Aedeagus largely devoid of scales, with large lateral pair of forward-pointing lateral spines.

DESCRIPTION: Coloration: (based on male only) Head: frons almost unicolorous, with faint differentiation among sclerites; frontal vitta finely striate, golden; ocellar triangle with lateral sides slightly lighter (area between ocelli slightly darker), shiny; fronto-orbital plate slightly lighter than vitta, shiny. Antenna: Scape light yellow, pedicel slightly darker, basal flagellomere dark yellow/tan, setulae very light, arista brown. Face light (very slight darkening at base of vibrissa), carina lighter; cheek, clypeus, palp, and proboscis light. Thorax: Scutum and scutellum evenly dark yellowish, pleura lighter; legs and halter very light, cream colored; wing faintly yellow. Abdomen: Tergites 1–5 each with completely transverse dark brown band on posterior half (tergite 1 with band lighter in middle), anterior half yellow, tergites 6, 7 all yellow. Sternites and epandrium light.

Head: Antenna: Scape with several fine setulae; pedicel with setulae and two larger setae; basal flagellomere short, apex not reaching oral margin, setulae very light, of moderate length (longest at apex of flagellomere); arista with 1 ventral, 7 dorsal branches, plus small terminal fork. Eye slightly egg shaped in lateral view, posterior margin slightly flattened; interfacetal setulae short, dense. Face of moderate height and depth, oral margin slightly concave; carina relatively well developed, narrow (ca. 0.8× greatest width of basal flagellomere), edge slightly flattened, length approximately 0.75× the face depth. One pair vibrissae; subvibrissal setulae very small; cheek of moderate depth; palp with single large, subapical seta. Frons: Sclerites best distinguished in anterior view of head; fronto-orbital plates narrow, shiny; frontal vitta narrow, minutely striate; ocellar triangle seemingly long and narrow, anterior corner reaching to slightly past level of proclinates. Frontoorbital setae: proclinate slightly shorter than posterior reclinate; anterior reclinate small, ca. 0.3× length of posterior reclinate; posterior reclinate slightly closer to proclinate than to inner vertical; ipsilateral proclinate, posterior reclinate and inner vertical setae in line, anterior reclinate slightly lateral to this tangent. Ocellar seta not reaching to proclinate; postocellar setae ca. 0.65× length of ocellar, crossed at tips. Vertical setae long, equal length; inner verticals upright, inclinate; outer verticals lateroclinate, pointed slightly posteriad.

Head measurements: CD / ED 0.15, ED / EW 1.40, FD /FW 0.97, FL / LFW 1.02, HW / HD 1.31, Ocellar S-index 1.80, OR1/OR3 0.94, OR2/OR1 0.38, VT-index 1.12.

Thorax: Setation: Acrostichal setae in 8 rows, with short, graded row larger acrostichals immediately anterior to dorsocentrals (acrostichal closest to anterior dorsocentral nearly equals its length). Anterior dorsocentral 0.65× length of posterior dorsocentral; posterior dorsocentral about midway between anterior dorsocentral and scutellar margin. Anterior scutellar setae divergent, equal in length to posterior scutellars, latter crossed at apical third. Postpronotal lobe with 2 setae; 3 notopleural setae (two lost, relative lengths unknown); 2 supra-alar setae (posterior one very long) [postalar, katepisternal setae lost from specimen]. Legs: Fore femur with ventral row of 4 long setae, lateral row of 4 long setae; longest setae greater than width of femur; male fore tarsus without fine, erect setulae on dorsal surface. Mid and hind femora without long setae; mid tibia with large ventroapical seta; hind tibia with short, fine preapical-dorsal seta.

Thorax and wing measurements: 4-V index 1.90, 5-X index 1.59, C-index 2.77, DC-index 0.65, hb-index 2.65, ThL 1.07, ThL/WL 0.47, WL/WW 2.28.

Male Terminalia: Epandrium arched, with microtrichia on dorsal half only; dorsolateral row of 5–6 setae, ventral lobe with group ca. 14 setae; lobe thick, short, not reaching to ventral margin of surstylus. Subepandrial lobe wide and short. Cercus not connected to epandrium; entirely microtrichose and setose; ventral margin with fine setulae on mesal corner. Surstylus pendulous, simple, with dorsolateral row 8 peg prensisetae, ca. 12 spiniform prensisetae more medially. Hypandrium well developed, relatively long, almost reaching to apex of aedeagal apodeme; posterolateral lobes turned inward, not wrinkled; paraphysis short, broadly and shallowly protruding, with microtrichia on mesal surface, large seta near middle. Aedeagus slightly longer than aedeagal apodeme, straight in lateral view; with lateral pair of large, forward-pointing, hooklike lobes; aedeagus with few, sparse scales toward apex. Female Terminalia: Unknown.

TYPES: Holotype male, on label: D. orbospiracula male, Chisos Mts. Texas, Mainland & Wagner Collectors, 1941, Type. In publication: “Upper Oak Creek, Chisos Mountains, Brewster County, Texas, August 13, 1941 ” (Patterson and Wheeler, 1942). Type in AMNH, the genitalia of which I have dissected.

OTHER SPECIMEN(S) EXAMINED: Patterson and Wheeler (1942) mentioned that a female was collected with the holotype male, but I have not found that specimen. The only other specimen is another male from the same locality as the type (1232.1 in the field notebooks), mounted on two glass slides: one slide with the legs, wings, and antennae, the other with genitalia.

COMMENTS: The abdominal color pattern is most similar to that of H. chagrinensis , but the opposite sexes of both species can be easily separated since chagrinensis has the basal flagellomere and palps dark brown (vs. yellowish), and a carina that is much smaller (in fact, barely present). Patterson and Wheeler (1942) described the internal reproductive organs of the male and female, the puparium, and metaphase chromosomes of H. orbospiracula . In lieu of specimens I cannot confirm the record from Hidalgo, Mexico, reported by Patterson and Wheeler (1942) and cited by Vilela and Bächli (2004).

Figures

FIG. 9. Hirtodrosophila orbospiracula (male holotype). A. Head, oblique frontal. B. Habitus, lateral. C. Head and thorax, dorsal. D. Thorax, oblique dorsal, showing enlarged acrostichals anterior to dorsocentrals. E. Abdomen, dorsal.

FIG. 16. Wings.

FIG. 29. Hirtodrosophila orbospiracula, male holotype. A. Frons, portion. B. Antenna. C. Aedeagus and aedeagal apodeme, lateral. D. Epandrium and associated structures (subepandrial sclerite shown detached, in full ventral view). E. Surstylus. F.Apex of aedeagus. G. Hypandrium, aedeagus, aedeagal apodeme.