Metrica Matson, 2022

Matson, Tanner A., 2022, A New Monotypic Genus from the American Southwest to accommodate “ Semiothisa ” kuschea (Geometridae: Ennominae), Zootaxa 5093 (1), pp. 67-74 : 68-71

Metrica Matson , new genus

( Figs. 1 , 5, 6 , 9 )

http://zoobank.org:act: 51F6B103-5D49-4246-AC0F-E2AE1C7E4C9F

Type Species: Metrica kuschea , original designation, monotypy.

Diagnosis. As the genus is so far monotypic, diagnostic characters entirely match those of the only species. The taxonomic identity of Metrica ’s closest known relative is uncertain ( Fig. 7 , see Discussion), though the two taxa are so different as to not warrant confusion. In North America, Metrica is superficially similar to Euaspilates spinataria Packard ( Fig. 3 ) or Eriplatymetra coloradaria (Grote & Robinson) ( Fig. 4 ) and Eriplatymetra lentifluata Barnes & McDunnough. Metrica males have filiform antennae, those of the previous species are bipectinate. Metrica lacks the darkened, costobasal gray patch present on the forewing of Euaspilates spinataria , and so far as known, the two moths are wholly allopatric; Metrica kuschea is confined to the Madrean sky islands and Euaspilates spinataria is a Rocky Mountain taxon with a range that extends into western Kansas and Nebraska. Eriplatymetra coloradaria and E. lentifluata lack the darkened subterminal and marginal bands of the forewing found in Metrica . In superficial aspect, Metrica kuschea may also appear similar to the Old World Megaspilates mundataria (Stoll) ( Fig. 2 ), though the two species do not appear to be closely related and do not overlap in range.

In North America north of Mexico, the genitalia of Metrica appear close to those of Caripeta and kin. Metrica exhibits a single, elongate, left-directed (right in ventral image view) juxtal+annular extension (the furca) that bows posteriorly toward the fused distal lobes of the gnathos; in this way, much like North American Caripeta . While Metrica has much reduced, sclerotized, fused distal lobes of the gnathos bearing only slight spination, the distal lobes of Caripeta are quite large and densely spinate. Most species of Caripeta have a dense patch of small cornuti, in Metrica , cornuti appear to be absent. In female Metrica , the large ventral flap created by the folded sternite of A8 is more or less symmetric over a centered ostium, yet in Caripeta this flap is often asymmetric with the right portion (left in ventral image view) of the flap rounded and more developed opposite a left-directed ostium. Metrica , Caripeta , and related Ennomini genera have swollen hindtibiae bearing a rosette of long androconia that fold into a longitudinal groove on the mesal surface—although at what level this character will prove to be phylogenetically informative is not yet known. The genetic data published herein also readily diagnose this taxon.

Description. Adult: ( Figs. 1 , 5 ). Head: Antenna filiform. Frons and vertex off-white, finely scaled. Labial palpus short, subequal to diameter of eye. Proboscis well-developed. Chaetosemata well separated. Thorax: Creamcolored. Foreleg with large epiphysis; tibial spur formula 0–2–4; hindtibia swollen, bearing plume of long androconia folded into longitudinal groove on inner surface (when not deployed). Forewing: Cream, darkened along subcostal area, and with four, brown transverse bands located respectively at antemedian, postmedian, subterminus, and outer margin. Antemedial band oblique, running subparallel to costa, diffusing, and hooking basally into darkened subcostal area at median; tiny brown discal spot situated basal to antemedial band in subcostal area. Outer margin band more diffuse and less defined than other bands, especially distally. Some light speckling along costa. Underside concolorous with upperside, but without bands (although banded patterning does show through). Subcostal area noticeably darker and given to brown. Hindwing: Concolorous with forewing. Brown discal dot present on both sides of wing. Upperside variable, but often with subterminal, transverse brown band ending before apex. Light brown speckling often present between subterminal band and outer margin. Abdomen: Cream. Cavi tympani globular, well separated, with ansa stout, swollen at base, narrowing and arcing in distal two-thirds, and flattened at apex. Male genitalia: ( Figs. 1C, 1D ) (n=2) Uncus slender, tapering medially to appear slightly spatulate. Arms of gnathos fused mediodistally bearing slight spination. Valve with pronounced costal sclerite spanning entirety of costal margin, costal sclerite inwardly falcate at apex. Anellus weakly sclerotized forming shallow pouch between arms of tegumen; furca (derived from both anellus and juxta) asymmetric, left-directed, one-half length of valve, and bearing apical setae that appear to interact with gnathal lobes; juxta with small digitate cavity directed anteriorly near saccus. Phallus slender with basal digitate heel; without cornuti. Female genitalia: ( Fig. 1B ) (n=2) Anterior apophysis one-third length of posterior apophysis. Sternite of A8 well sclerotized around ostium bursae, folded transversely to create large ventral flap. Ostium with ventral, transverse triangulate sclerite; ductus bursae short. Corpus bursae pyriform with two signa: first signum situated posterodorsad, near junction with ductus bursae, amorphous, transversely extended, and indented to appear cup-like; second signum as in several related genera, circular, inwardly depressed, positioned anteroventrally, and bearing many inward-directed spines.

Biology. Metrica kuschea is known only from the high elevations (> 8000 ft) of the Chiricahua mountains of southeastern Arizona, USA , but may also inhabit undersampled areas of the northern reaches of Mexico’s Sierra Madre Occidental. The taxon is single-brooded with an adult flight centered in June and July in Arizona.

In July of 2016, John Palting of Tucson, Arizona, egged a gravid female of Metrica kuschea that yielded many eggs which were subsequently split between himself and David Wagner (UConn). Neonates were offered a buffet of host options that grow at or near the collection site. Palting offered Abies, Cercocarpus , Holodiscus, Mertensia , Penstemon, Pinus, Populus, Prunus, Ribes, Rosa , and Rubus , all without success. Wagner tried Abies , Amphiachyris dracunculoides , Holodiscus , and Penstemon barbatus , he too, without success.

In July of 2021, John Palting, egged a second gravid female—this time with moderate success as he was able to establish larvae on a potted plant of aspen fleabane ( Erigeron speciosus ) ( Asteraceae ), a widespread, native, western North American species found at mid to high elevations in the Chiricahua mountains. The brown caterpillars predominantly fed at night, resting off plant attached to the mesh over his potted plant by day. Unfortunately, no larvae were imaged; early instars defoliated John’s single plant, and while attempting to garner fresh host foliage, John was stymied by monsoonal floods—all larvae would eventually perish at about one centimeter in length after being switched to spreading fleabane ( E. divergens ). The immediate hatching of both clutches of eggs suggests that caterpillars typically follow the adult flight with larvae likely present from July through August, and that the pupa overwinters.

If Metrica kuschea proves to be a dietary specialist on Erigeron , it is unlikely that it would feed exclusively on E. speciosus . Several rarer and more geographically limited species of Erigeron may also host M. kuschea —perhaps one or more of these species proving to be more preferred. The Chiricahua mountains are home to six native Erigeron species , all of which may co-occur above 8000 ft ( Bennett et al. 1996). Ironically, the rarest of these, a high-elevation species restricted exclusively to the Chiricahua mountains, is Erigeron kuschei —yes, like the specific epithet of Metrica kuschea —a patronym to honor the original collector of both species, John August Kusche.

Etymology. The new genus name, Metrica , relates to the geometric lines of the forewing of the only known species, Metrica kuschea , and the geometrid family to which this taxon belongs.

Remarks. Molecular data place Metrica among the Ennomini following the synonymization of the previously recognized Ourapterygini ( Beljaev 2008, Sihvonen et al. 2011; Brehm et al. 2019). Metrica shows a well-supported sister relationship to a Neotropical lineage of “ Isochromodes ” ( Figs. 7 , 9 , see Discussion).

Figures

FIGURE 1. Adult Metrica kuschea. A, C, D, USA: AZ: Cochise Co., Chiricahua Mts., Long Park above Rustler Park (FR 42D), Elev. 9160’, 30 June 2015, coll. J. Palting, Genetic Voucher(s): DLW-001745, TAM0223, Genitalic Voucher: TAM-2021-098; A, dorsal habitus; B, female genital (PARATYPE), USA:AZ: Cochise Co., Chiricahua Mountains, Turkey Flat, 8-9000’, 22 July 1927, coll. J.A. Kusche, USNM 131357; C, male genital capsule; D, male phallus. Images not to scale.

FIGURE 9. Phylogeny of Ennomini genera with voucher IDs from IQ-TREE analysis. SH-like support values are followed by ultrafast bootstrap (UFBoot2) support values.

FIGURES 5–8. Type specimen and molecular voucher images. 5, HOLOTYPE male of Semiothisa kuschea, and 6, label data (image credit Chris Grinter); 7, voucher image of “Isochromodes” “infida” (GB-CR-1241), sister taxon of Metrica misidentified as Certima dositheata in Murillo-Ramos et al.(2019) and Brehm et al.(2019) (image taken from, and image credit to, Supplement File 5 of Brehm et al. (2019)); 8, SYNTYPES of Sabulodes infida from USNM type search (https://collections.USNM.si.edu/ search/ento/). Images not to scale.

FIGURES 2–4. Dorsal habitus of taxa superficially similar to Metrica but not closely related. 2, Megaspilates mundataria, [Eurasia], location label unintelligible, Genitalia Slide: USNM57223; 3, Euaspilates spinataria, USA: New Mexico: Harding Co., 1mi. S. of Mills Cyn. Campground (036 01’ 52.7” N, 104 21’ 43.2” W), Elev. 5120’, 21 July 1998, coll. J.D. Hooper; 4, Eriplatymetra coloradaria, USA: Colorado: Chaffee Co., 4 mi N of Buena Vista, Elev. 8500’, 14 July 1982, coll. Douglas C. Ferguson. Images not to scale.