Microcercis minor (Adams), 2024

Foster, George A., 2024, Revision of Nearctic Microcercis Beschovski (Diptera: Chloropidae), with Synonymy of Incertella Sabrosky, Zootaxa 5481 (4), pp. 401-439 : 415-417

Microcercis minor (Adams)

( Fig. 9 , 20 , 33, 34 )

Oscinis minor Adams, 1905: 110 . Type locality: Opelousas, Louisiana. Deposited FMNH. NEW COMBINATION.

Oscinella minor .— Becker 1912: 104, 107, 118 [in key, description].— Sabrosky 1935: 258, 264, 256, 267 [key and discussion including a brief description and biological notes].— Sabrosky 1936: 713 714, 725 726 [Division B in key, discussion of type material, distribution].— Sabrosky 1965: 780 [catalog].

Botanobia (Oscinis) proxima, Malloch, 1914: 25 .— Malloch 1915: 162 [syn. of minor ].

Incertella minor .— Sabrosky 1980: 421 [placement in Incertella ].— Sabrosky and Paganelli, 1984: 18 [ Mexico record, Nuevo León].— Foote 2007: 11 [assoc. with damaged stems of spike rush, Eleocharis palustris in Ohio].

Diagnosis.—Ocellar triangle yellow except ocellar tubercle gray to black, evenly tomentose; vertex light grayish yellow; occiput gray to black; postpedicel dorsal one third to one half black, remainder yellow; prosternum bright yellow; scutum ground color yellow anteriorly, gray posteriorly, entirely tomentose; postpronotal lobe yellow, tomentose; notopleuron mostly light gray to yellow, tomentose; pleuron mostly to entirely yellow, katepisternum and meron may be mostly brown, ventral polished area continuous from propleuron to meron; legs various from mostly yellow with dark spot on central portion of hind femur and tibia to mostly dark gray, tarsi dark; tibial organ light gray to yellow; syntergite 1+2 usually yellow with brownish spots medially and laterally, remaining tergites brown with yellow posterior margins; male cerci small, rounded triangulate; surstylus long, narrow, parallel sided, distally rounded with angulate tip.

Description.—Body length; female: 1.18−1.68 mm; male: 1.10−1.47 mm.

Head: Ocellar triangle dull grey to blackish only on the ocellar tubercle, the remainder yellow to orange, tomentose; vertex light grayish yellow; occiput dark gray to black tomentose dorsally, becoming orange/yellow ventrally; frons yellow; scape and pedicel yellow, postpedicel dorsal one third to one half black, remainder yellow; arista black, pubescent; face, palps, gena and clypeus bright yellow; prementum polished brown, labellum light to dark brown; gena to eye ratio 0.20.

Cephalic chaetotaxy: Fronto-orbital setae dark brown to black; interfrontal setae brown; ocellar setae gray to black; postocellar setae gray to black; outer vertical setae gray to black; inner vertical setae gray; postocular setae short, fine, gray to black; vibrissae yellow; subgenal setae yellow.

Thorax: Prosternum bright yellow; prescutum polished black; scutum with yellow setulae, gray tomentum over a yellowish ground color anteriorly becoming a gray ground color posteriorly; postpronotal lobe yellow; notopleuron light gray to yellow, tomentose; pleuron mostly to entirely yellow, katepisternum and meron may be mostly brown, ventral polished area continuous from propleuron to meron; anatergite light gray and lateral portions of mediotergite darker and more densely gray tomentose, mediotergite black and lightly tomentose centrally; scutellum mostly gray, tomentose medially with margin yellow, yellow color sometimes only visible from posterior view; subscutellum with light gray tomentum; wing length 1.16–1.56 mm, hyaline, costal ratios 0.43:0.27:0.19; legs various from mostly yellow with dark spot on central portion of hind femur and tibia to mostly dark gray, tarsi dark; femoral organ as in figure 9; tibial organ light gray to yellow.

Thoracic chaetotaxy: Scapular seta absent; scutal and scutellar setae yellow to black.

Abdomen: Syntergite 1+2 mostly yellowish with brownish areas medially and laterally; remaining tergites brown centrally, yellow along the posterior margin and lateral edges, with many scattered yellowish setulae. Male terminalia (figs. 33, 34): epandrium black tomentose, cerci small, rounded triangulate; surstylus long, narrow, parallel sided, distally rounded with angulate tip. Female cerci and preceding segment black, contrasting with bright yellow terminalia.

Distribution.—Nearctic: Canada (Manitoba, Ontario, Saskatchewan). Mexico (Nuevo León). United States (Alabama, Arizona, Arkansas, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Vermont, Wisconsin, Wyoming).

Discussion.—This species is distinguished from most other Microcercis species by its mostly yellow, ventrally polished, pleuron and yellowish to mostly gray scutum. Also, the male surstyli are longer than the other species of Microcercis .

I have mostly found this species on lawns and other grassy areas inland but have seen some material from coastal marshes and beach dunes. I usually only find a few specimens at a time, the most being eight specimens from a grassy lawn area at the entrance to the Alpha Ridge Landfill in Howard County Maryland .

Sabrosky (1935) reports that M. minor can be extremely common in Kansas (nearly one half of all the M. minor material examined for this study came from Kansas, likely due to the heavy collecting done there in the 1930s by Sabrosky and others), and it has often been taken sweeping pasture grasses and wheat. He also notes that it has been reared from wheat and that the species has three generations per year beginning in April and continuing to November. Additional records (below) indicate that it has also been reared from barley, corn, Elymus , Stipa , and the egg pod of a grasshopper, Melanoplus bivittatus ( Say, 1825) . The latter record is unconfirmed and likely doubtful.

Based on the material examined from multiple states, M. minor seems to be the most common and ubiquitous species of the genus in North America. Fresh specimens are orangish, becoming more yellow with drying and ageing, and there is a less common form that shows a darker mesonotum, pleuron, and legs.

Adams (1905) based his description on four specimens from Opelousas, Louisiana without designating any one of them as the holotype. Sabrosky (1936) having found and examined them in the Hough Collection of the Field Museum of Chicago, designated a female of the series as lectotype but gave no more information.

Figures

FIGURES 9–14. Microcercis and Conioscinella morphology. 9, M. minor male femoral organ, 2500X. 10, M. infesta male femoral organ, 3000X. 11, C. nuda male femoral organ, 2000X.12, M. infesta male genitalia, 500X, (arrow points to epandrium). 13, M. infesta hind basal tarsomere (arrows indicate basal setae). 14, C. ovalis hind basal tarsomere.

FIGURES 15–22. Microcercis morphology. 15, M. albipalpis habitus, lateral view. 16, M. bispina habitus, lateral view. 17, M. dorsata habitus, lateral view. 18, M. infesta habitus, lateral view. 19, M. insularis habitus, lateral view. 20, M. minor habitus, lateral view. 21, M. johanni habitus, lateral view. 22, M. murphyi habitus, lateral view.

FIGURES 31–38. Microcercis and Conioscinella morphology. 31, M. insularis male genitalia, posterior view. 32, M. johanni male genitalia, posterior oblique view. 33, M. minor male genitalia, posterior view. 34, M. minor male genitalia, lateral oblique view. 35, M. murphyi male genitalia, posterior oblique view. 36, M. murphyi male genitalia, lateral oblique view. 37 M. trifeminarum male genitalia, posterior oblique view. 38, C. ovalis male genitalia, posterior oblique view.