Cerodontha (Butomomyza) enigma, 2019

Eiseman, Charles S., Lonsdale, Owen & Feldman, Tracy S., 2019, Nine new species of Agromyzidae from North Carolina, USA, with new host and distribution records for additional species, Zootaxa 4571 (3), pp. 301-333 : 308-309

Cerodontha (Butomomyza) enigma spec. nov.

( Figs. 9–10 , 37 , 68–73 )

Holotype. NORTH CAROLINA: Durham Co., Durham, Pelham Road , 14.v.2017, em. 4.vi.2017, T.S. Feldman, ex Dichanthelium dichotomum ssp. nitidum , # CSE3790 , CNC939826 (1♂).

Etymology. The specific epithet refers to the quandary posed by this unique specimen, which is so similar to Cerodontha angulata (Loew) in both leaf mine and adult morphology.

Host. Poaceae : Dichanthelium dichotomum (L.) Gould.

Leaf mine. ( Fig. 37 ) The mine of the single known specimen was primarily on the upper leaf surface, where it consisted of irregular elongate branches and was mostly whitish and greenish with a few patches of reddish discoloration. A small area toward the apex of the lower leaf surface was also mined, forming an irregular whitish patch with dark frass in several small lumps and grains.

Puparium. ( Fig. 10 ) Oval, reddish-brown; formed within the mine.

Distribution. USA: NC.

Adult description. Wing length 2.4 mm (♂). Female unknown. Length of ultimate section of vein M 4 divided by penultimate section: 0.8. Costa extending to M 1. Eye height divided by gena height: 22.0. First flagellomere small, rounded, apical margin with longer hairs. Frontal vitta minutely textured. Ocellar triangle not evident. Lunule velvety, shape typical of other Butomomyza. Thorax subshining.

Chaetotaxy: Two ors, two ori, becoming shorter anteriorly. Orbital setulae short, numerous and closely spaced. Postvertical and ocellar setae subequal to ori. Five dorsocentral setae, fifth seta presutural, first much stronger; second seta approximately? length first seta, fifth seta approximately ½ first seta; first pair of setae widely spaced, setae pairs two to five convergent posteriorly with second pair strongly inset. Acrostichal seta subequal to anterior dorsocentral. Acrostichal setulae in approximately six to eight scattered rows. In addition to upcurved dorsomarginal setae typical of subgenus, katepisternum with additional dense cluster of upcurved setae anteroventral to base of dominant seta. Mid tibia with two posteromedial setae.

Coloration: ( Fig. 9 ) Setae black. Body dark brown with calypter and halter yellow; frons, lunule and gena brownish-beige with ocellar tubercle dark brown, lateral margin of orbital plate brown and posterolateral corner of frons to base of inner vertical seta dark brown; wing veins light yellow, only brown apically; apex of fore femur light yellow with spot as long as wide; fore tibia light yellowish-brown; tarsi light yellow with apical two segments browner.

Genitalia: ( Figs. 68–73 ) Epandrium very broad with small, rounded supra-anal process directed posteriorly. Surstylus small, fully fused to inner anteroventral margin of epandrium and not visible laterally; with irregular vertical row of six or so long tubercle-like setae. Subepandrial sclerite mostly reduced to one pair of dark, widely divided, curved ventral arms with strong outer subapical points. Hypandrium strongly arched, arms narrowest medially, with sclerotized marginal band and anteromedial line; inner lobe narrow, transverse, anterior margin irregular, several fossae present near base; arm of hypandrium basal to inner lobe strongly reduced. Pregonite narrow, darker and rounded apically. Phallophorus cylindrical, slightly elongate. Basiphallus short, not much longer than phallophorus, halves approximate on medial left-dorsal surface; left sclerite weak and ill-defined (more so apically), base slightly more ventral in position, apex wider with dorsal margin produced and irregular; right sclerite broadest medially, apex narrowed and strongly deviated, extending along right surface past base of mesophallus. Hypophallus large, trilobed and membranous with long, narrow medial tubule that is anterobasally sclerotized and extends around apex of medial lobe; right lobe with broad, weak diffuse sclerotization basally; sclerite on left lobe more well-defined, darker to base; left lateral margin past sclerite with additional faint medial and subapical sclerotizations. Paraphallus lobate, almost spherical with posteroventral sclerotized patch; left paraphallus with additional lobe that is similarly spherical and with a ventral, transverse sclerotized patch that is narrowed medially and posteriorly connected to patch on ventral lobe. Mesophallus dark, narrow, nearly as long as basiphallus, and divided into long basal stem and apical bulb; width of stem less than one fifth length, with shallow, weak distoventral carina; bulb slightly more than one third length of stem, basal margin appearing bilobed when viewed ventrally, length and height subequal, width greater by one half; space between mesophallus and distiphallus equal to length of mesophallus bulb. Distiphallus entirely divided into two long, dark tubules that are directed dorsally, slightly diverging apically, shallowly sinuous, and as long as mesophallus; apex slightly wider and straighter, shallowly bulging subapically; distal curve minutely textured dorsally. Ejaculatory apodeme not found.

Comments. While superficially similar in overall appearance to other Butomomyza, Cerodontha enigma differs strikingly from all related taxa in two aspects of chaetotaxy: there are five dorsocentrals, with the posterior pair widely spaced and the anterior four pairs converging posteriorly; the katepisternum has a dense cluster of long upcurved setae anterior to the base of the dominant seta. Furthermore, the gena is exceptionally narrow, and while the genitalia are similar to those of other locally occurring species, including the relatively common C. angulata (see Spencer & Steyskal (1986: Figs. 583–586)), there is a small supra-anal process, the left paraphallus is bilobed, the mesophallus is longer with a smaller apical lobe and the distiphallus is straighter.

We have repeatedly reared Cerodontha angulata from similar mines on Dichanthelium spp. in both Massachusetts and North Carolina ( Eiseman & Lonsdale 2018). In that species the mine usually begins with a dark, trumpet-shaped area along the midrib, and the larva initially mines toward the apex of the leaf. A single blackish patch of frass is deposited at the point where the larva reverses direction. CSE has also found a single presumed C. angulata mine that was formed entirely on the lower surface, but no individual has been observed to mine both leaf surfaces. Since the present mine description for C. enigma is based on a single example, additional rearings will be required to characterize this species in comparison with C. angulata .

Figures

FIGURES 7–14. FIGURES 7–8. Calycomyza chrysopsidis spec. nov.; 7: male; 8: empty puparium in opened mine. FIGURES 9–10: Cerodontha (Butomomyza) enigma spec. nov.; 9: male; 10: empty puparium. FIGURES 11–12: Cerodontha (Poemyza) arundinariella spec. nov.; 11: male; 12: larva and puparium in mine. FIGURES 13–14. Cerodontha (Poemyza) saintandrewsensis spec. nov.; 13: male; 14: empty puparium.

FIGURES 33–40. leaf mines; 33: Calycomyza chrysopsidis spec. nov. on Chrysopsis mariana, reflected light (puparium at leaf base); 34: same, transmitted light (puparium at lower right); 35: C. novascotiensis Spencer on Scutellaria integrifolia, initial serpentine portion (reflected light); 36: same, completed mine (transmitted light); 37: Cerodontha (Butomomyza) enigma spec. nov. on Dichanthelium dichotomum; 38: Cerodontha (Poemyza) arundinariella spec. nov. on Arundinaria tecta (transmitted light); 39: Cerodontha (Poemyza) saintandrewsensis spec. nov. on Arundinaria tecta; 40: Phytomyza plantaginis Robineau-Desvoidy on Plantago wrightiana (transmitted light; puparium in middle of leaf).

FIGURES 68–73. Cerodontha (Butomomyza) enigma spec. nov., male genitalia; 68: external genitalia, anterior; 69: external genitalia, left lateral; 70: postgonite; 71: hypandrium; 72: phallus, ventral; 73: phallus, left lateral.