Omphalophora Becker, 1900

Kerr, Peter H., 2010, 2592, Zootaxa 2592, pp. 1-133 : 91-94

Genus Omphalophora Becker

Figs. 13–14, 52–53, 75–76, 97–98, 120, 143–144, 161–162.

Omphalophora Becker 1900: 12 . Type species Omphalophora oculata Becker 1900 , by monotypy.

Diagnosis. The monophyly of Omphalophora is supported by the unique form of female tergite 9, which is distinctively bulbous and tapers posteriorly. Partially sclerotized lobes located in the membrane between the ninth tergite and ninth sternite may also be a synapomorphy for the group. Omphalophora and Ptiolina are very similar in their antennal form and general habitus, but phylogenetic analysis reveals that they form a paraphyletic grade when grouped together.

Omphalophora species are delicate to fairly robust flies, small to moderately sized (3.0 to 10.0 mm) that are entirely black or brown in color. Wings are hyaline or infuscate near wing veins; male holoptic, eyes separated in female; antenna with unsegmented terminal stylus, round or lightly laterally compressed in cross section; mandibles absent; laterotergite bare; anepisternum setose; M 3 present; tibial spur formula 0:2:1; hind tibia without macrochaetae; female tergite 7 longer than wide; female tergite 9 with ventrolateral arms, extending posteriorly, surrounding and fusing to sternite 9 laterally; spermathecal ducts with accessory glands. Omphalophora is restricted to the Holarctic Region. Omphalophora is easily confused with Ptiolina . It may be distinguished from this genus by having a setose anepisternum, veins R 4+5 containing the wing tip, female tergite 7 clearly longer than wide (in Ptiolina , this tergite is clearly wider than long), and in the male, the tergite 10 is as wide as long or nearly oval and the gonostylus comes to a sharp point apically. For more details on the differences between Omphalophora and Ptiolina , see discussion below. Omphalophora may be confused with Symphoromyia but are immediately distinguished by having the scape approximately the same size as the pedicel, first flagellomere longer than wide (elongated anteriorly, not reniform), and bare laterotergite. Omphalophora may be distinguished from Bolbomyia by the unsegmented style, by the absence of fore tibial spurs, and by having vein M 3 present. Omphalophora is usually significantly larger than Spania and also differs by having a hind tibial spur.

Description. Head. Clypeus bulbous. Scape approximately same size as pedicel. First flagellomere lightly compressed laterally or rounded in cross section (may vary from specimen to specimen), bearing stylus of single segment. Eyes inconspicuously setulose; in female, dichoptic; in male, holoptic, not strongly flattened dorsally, ommatidia evenly distributed, gradually smaller toward ventral margin. Labella with pseudotracheae, length variable. Theca short and stout, with medial suture. Palpus one- or two-segmented. When two-segmented, distal palpomere longer than proximal segment. Stipes surrounded by membrane above theca, directed posteriorly. Lacinia present, shorter than palpus, not serrated at tip. Mandibles absent. Cibarial pump short, as long as wide or slightly longer than wide. Cornu shorter than cibarial pump. Pharyngeal pump narrow along most of length, mostly flat, approximately same length as cibarial pump.

Thorax. Mesonotum usually with vittae, but may be without. Dorsocentral bristles absent; all dorsal setae of equal length. Anepisternum setose throughout posterior half. Laterotergite bare. Proscutellum usually present. Subscutellum not enlarged nor lengthened; inconspicuous. Wing hyaline or lightly infuscate, without markings. Costa extends to R 5, at wing tip. Lower calypter reduced. Upper calypter well developed, with broad curvature, lobe-like, width twice length or less. Humeral crossvein well developed. Sc-r crossvein weakly developed, positioned distal to h by approximate length of h or more. Dorsal side of R 1 setulose, ventral side bare. All other wing veins without setulae. R 1 and R 2+3 separated by various degrees at wing margin. R 2+3 sinuous, apical third of R 2+3 ultimately bends anteriorly slightly, toward leading edge of wing margin. Base of R 4 –R 5 fork proximal or directly above distal end of cell dm. R 4 nearly straight apically or curving slightly towards anterior margin. R 4 and R 5 contain wing tip. R 5 clearly longer than R 4+5 (r-m to R 4 origin). R-m crossvein at proximal one-fifth to near halfway of discal cell. M 3 present. M-cu crossvein present. Origin of CuA 1 at cell bm. CuA 2 greater than 1/2 length, less than 2/3 length of posterior vein of cell bm. Anal lobe well developed. Alula full, rounded with broad curvature. Cell cu p open or closed. Halter knob between 1/2–2/3 length of stem. Tibial spur formula 0:2:1. Hind tibial spur short. Hind coxal tubercle absent. Hind tibial macrochaetae absent (long delicate setae sometimes present). Postmetacoxal bridge absent.

Abdomen. Abdominal segments evenly tapered. In female, last 3 abdominal segments telescoped; tergite 7 much wider than long; intersegmental membrane between segments 7 and 8 especially long; sternite 8 as wide as long or wider than long. Male terminalia with epandrium simple, not containing hypandrium ventrally. Epandrium wider than long, modestly curved anteriorly. Tergite 10 present, undivided, narrow (clearly wider than long), setose. Hypoproct present, setose. Cercus base held underneath epandrium, or directly adjacent to epandrium. Cerci displaced from one another, separation distance greater than three quarters width of cercus. Cerci, in posterior view flat or cupped, forming circular outline medially. Hypandrium fused entirely to gonocoxites. Gonocoxite with sinuous dorsal ridge, leading to gonocoxal apodeme. Gonocoxal apodemes short or long enough to reach anterior margin of hypandrium. Sperm sac forming separate, distinct lobes ventrally. Lateral ejaculatory processes present, not part of sperm sac posteriorly. Ejaculatory apodeme short or moderately long, reaching anterior margin of hypandrium in some species. Ejaculatory apodeme rodshaped or laterally compressed. Aedeagal tines absent. Endoaedeagal process present; short, blunt, rounded. Female sternite 8 longer than wide. Female terminalia with tergite 9 entire, with anteriorly-directed ventrolateral projections, attached to and enveloping sternite 9. Spermathecae three, clubbed, sclerotized. Spermathecal ducts more than three times but less than five times length of sternite 9, not inflated at base of spermathecae. Spermathecal duct accessory glands arise at approximately distal third of the spermathecal ducts. Spermathecal ducts near junction with common duct not sclerotized. Common spermathecal duct thickened; of moderate length, about same length as longest diameter of genital chamber. Genital chamber oval, moderately sized. Accessory gland posterior to genital chamber inconspicuous, easily overlooked even after staining. Accessory gland posterior to genital chamber common duct present with short paired extensions posteriorly. Sternite 9 anterior end narrowly paddle-shaped, posterior end with broad extensions posteriorly, joined together in horizontal plane centrally, held in vertical plane laterally. Tergite 10 entire; short, length less than half width. Sternite 10 sclerotization weakened centrally, making it appear as if sclerite divided into two lateral components. Sternite 10 roughly rectangular or ovoid, pointed posteriorly. Cercus two-segmented. First segment of cercus not elongate, without ventral process. Ventral lobes of first segment of cercus not curving ventrally towards one another to form ring. Basal cercal segment separated from one another dorsally by approximate width of the second cercal segment. Second cercal segment narrow, elongated (~3x longer than wide or more), with apical sensory pits.

Larva. Unknown.

Biology. The biology of Omphalophora species is not known.

Literature. Omphalophora species descriptions and treatments are almost entirely contained within the body of work covering the genus Ptiolina . Hardy & McGuire (1947) provide a key to North American species. Narchuk (1969) gives a key to eastern European species.

Notes. In 1900, Becker established Omphalophora oculata , a new genus and species from West Siberia. Frey added Omphalophora lapponica ( Frey 1911) and another species was added later, when Szilády transferred Chrysopilus arctica Frey to the genus ( Szilády 1934a). Nagatomi (1982a) examined all three types of these species and determined that Chrysopilus arctica Frey was erroneously placed in Omphalophora by Szilády (1934a) and was a true Chrysopilus species , in agreement with Narchuk (1969). For the Omphalophora species , Nagatomi noted that R 2+3 is straight in its apical portion, wing cell sc is wider at wing margin than r 1, R 5 at wing margin beyond wing tip and the posterior cubital cell (cu p) is open. These features were believed to vary within Ptiolina , however, and he synonymized Omphalophora with Ptiolina . Majer (1988) did not recognize Nagatomi’s contribution and followed Szilády (1934a), keeping all three species in Omphalophora . Narchuk (1969) indicated that Omphalophora differed from Ptiolina by its larger size and having a reduced or absent hind tibial spur. In addition to O. lapponica and O. oculata , Ptiolina grandis Frey and P. uralensis Becker shared these qualities and were consequently placed in Omphalophora . Later, however, Nartshuk (1995) synonymized O. lapponica and P. uralensis with Omphalophora oculata (Becker) and at the same time, re-assigned Omphalophora to junior synonym status (= Ptiolina ). Nagatomi also treated Omphalophora as a synonym of Ptiolina ( Nagatomi 1982a) .

Perhaps because of their accessibility, the antennae often receive special attention in taxonomic treatments, and this is certainly the case for Omphalophora and Ptiolina . Species within these groups have obvious differences in antennal morphology. The first flagellomere in Omphalophora majuscula , for example, is rounded, enlarged and conical at its base then smoothly tapered into an extended stylus, somewhat reminiscent of the antenna of species in Litoleptis and Spaniopsis ( Fig. 14; compare with Figs. 11–12, 20–21). In many Ptiolina (e.g., P. edeta , P. zonata , and others), the first flagellomere is enlarged but flattened laterally, with a clear break between the stylus and the first flagellomere ( Figs. 15–16). However, enough overlap of antennal morphologies exists between Omphalophora and Ptiolina to break down the reliability of this character system. In Omphalophora species (at that time, represented by O. oculata and O. lapponica ), Nagatomi (1982a: 56) noted that R 2+3 is straight in its apical portion, wing cell sc is wider at wing margin than cell r 1 (“wing vein R 5 at wing margin beyond wing tip”), and cell cu p is open. Now that more species are added to Omphalophora based on male and female genitalic characters (discussed below), a greater understanding of the evolution of wing venation in the two groups may be developed. Vein R 2+3, for example, is not always straight in its apical portion in Omphalophora and cu p is not always open at the margin. At least one wing character consistently separates Omphalophora and Ptiolina , however. In Omphalophora , wing veins R 4 and R 5 contain the wing tip ( Figs. 52–53) whereas in Ptiolina , R 5 is anterior to the wing tip ( Figs. 54– 55). In many Omphalophora , R 2+3 is longer than the length of R 5, however this character is less reliable (in O. nigripilosa , R 2+3 is not obviously longer). In Ptiolina , wing veins R 2+3 and R 5 are either approximately equal in length, or R 5 is longer. Relative length of wing cells sc and r 1 is not a discrete and reliable feature distinguishing Omphalophora and Ptiolina .

Thoracic morphology is similar between the two groups, with one noticeable difference. The anepisternum of Omphalophora species is setose near the posterior margin whereas in Ptiolina , this sclerite is completely bare. Tibial spurs have been identified as a character that may assist separating Omphalophora and Ptiolina ( Narchuk 1969) . I could not find any meaningful differences in size, number, or placement of tibial spurs, however.

Omphalophora exhibit several distinctive characters in the male genitalia that instantly distinguish it from Ptiolina ( Figs. 75–78, 97–100). The most pronounced feature is that each gonostylus comes to a sharp point apically ( Figs. 97–98), as opposed to in Ptiolina , where the gonostylus is rounded apically ( Figs. 99–100). Omphalophora also have an elongate aedeagal sheath, posterior of the gonocoxites medially, where it narrows. In Ptiolina , the aedeagal sheath tends to be shorter. Similarly, the gonocoxal apodemes tend to be longer in Omphalophora than in Ptiolina . This feature is less striking and therefore, perhaps more difficult to distinguish without directly comparing samples. However, in all of the samples examined, the gonocoxal apodemes of Omphalophora reach the anterior margin of the hypandrium when examined in a direct dorsal view; in Ptiolina , the gonocoxal apodemes end well short of this. The epandrium is clearly different in Omphalophora , where tergite 10 is either as wide as long or squared and nearly oval (as in O. fasciata ) ( Figs. 75–76). Whereas in Ptiolina , tergite 10 is narrow rectangular, approximately three times as wide as long ( Figs. 77–78). The hypoproct is tomentose in Omphalophora , setose in Ptiolina . The epandrium is also much more firmly secured to tergite 10, and the cerci more firmly attached to the hypoproct, (in a single plane) in Omphalophora . In Ptiolina , the epandrial and subepandrial sclerites (tergites 9 and 10) tend to rest at a perpendicular angle, loosely attached, after being cleared and placed in glycerol. Separation between cerci seems to vary at the species level, independent of higher level patterns and the form of the epandrium (e.g., notching or curvature of the posterior and/or anterior margin) does not appear to resolve differences at the generic level. While a medial line of increased sclerotization of the epandrium (as evidenced by O. lapponica and especially O. majuscula ) is more common in Omphalophora (e.g., Fig. 76), it is an unreliable character to differentiate Omphalophora and Ptiolina .

In Omphalophora , the female tergite 7 is clearly longer than wide, whereas in Ptiolina this tergite is clearly wider than long. Tergite 9 in Omphalophora is bulbous laterally and tapers posteriorly, with a length that is greater than half its width. In Ptiolina , tergite 9 is rectangular and narrow; its length is less than half its width. Also in Ptiolina , the ventrolateral arms of tergite 9 are easily distinguished, forming a modest s-curve when observed in the dorsal/ventral perspective (e.g., Fig. 145). The distal, anterior tip of these ventrolateral arms is fused to sternite 9 to varying degrees (e.g., lightly fused as in P. zonata or firmly attached as in P. mallochi ), but for the most part, the arms of tergite 9 are free from sternite 9 posteriorly. There is no such separation in Omphalophora , where the ventrolateral arms are bound to sternite 9 by a thick membrane along their entire length. The form of sternite 9 itself differs significantly between Omphalophora and Ptiolina ( Figs. 143–148). In Omphalophora , sternite 9 is narrow posteriorly and then broadens as it extends anteriorly beyond the ventrolateral arms of tergite 9 and is broadly rounded apically (anteriorly). The genital chamber, formed at the base of the common spermathecal duct, is narrow, with lateral margins that are nearly parallel, in line with a lengthened common spermathecal duct. In Ptiolina , sternite 9 is widest posteriorly, within the ventrolateral arms of tergite 9, and extends anteriorly as a narrow, nearly parallel-sided process which is flat truncated at its anterior apex. Female genitalia of Omphalophora also have partially sclerotized lobes located in the membrane between the ninth tergite and ninth sternite. The origin and homology of these structures are unclear. They are absent in species of Ptiolina .

The genital chamber of Ptiolina species occupies a larger area and the margins of which are clearly oval (not nearly parallel sided as in Omphalophora ). The common spermathecal duct is reduced to a short length (less than the length of the genital chamber) in Ptiolina and the spermathecal ducts themselves are less than three times the length of sternite 9. Spermathecal duct accessory glands arise at or near the base of the sclerotized spermathecae (e.g., Fig. 147). In Omphalophora , the common spermathecal duct is lengthened to at least the same length as the genital chamber, or longer, and the spermathecal ducts are at least three times the length of sternite 9 or greater. The spermathecal duct accessory glands arise at approximately two-thirds to four-fifths the distal length (from sternite 9) leading to the spermathecae ( Figs. 161–162). The duct is wider and thicker between the accessory gland and the sclerotized spermatheca, suggesting that it may be an unsclerotized proximal expansion of the spermatheca. This is true for all taxa (in Ptiolina , see in particular, P. mallochi ; it is readily apparent in all Omphalophora ). Spermathecal form appears to vary on a species level and does not distinguish between Omphalophora and Ptiolina . Spermathecae may be oval, egg-shaped, or spherical, regardless of grouping. Spermathecal sclerotization is generally well developed in both groups. The degree of lateral displacement between the basal cercal segments is also variable at the species level and is inadequate for distinguishing between Omphalophora and Ptiolina (not to mention difficult to score objectively on account of its continuous nature).

Body size was an important consideration for distinguishing Omphalophora and Ptiolina in the past ( Hardy & McGuire 1947). This was probably attributable to the fact that the original species placed in Omphalophora are particularly large (e.g., O. oculata ). Their size, however, is largely independent of ancestry at the genus level. Omphalophora fasciata and Omphalophora nigripilosa , for example, are comparable in size to some of the smallest species in the Ptiolina .