Etainia thoraceleuca van Nieukerken, Epstein & Davis, 2024

van Nieukerken, Erik J., Davis, Donald R., Swain, Steven V. & Epstein, Marc E., 2024, A new North American species of Etainia (Lepidoptera, Nepticulidae), feeding on Arbutus and Arctostaphylos species (Ericaceae), ZooKeys 1193, pp. 195-218 : 195

Etainia thoraceleuca van Nieukerken, Epstein & Davis sp. nov.

Etainia albibimaculella ; van Nieukerken et al. 2016: 145; van Nieukerken 2018: 32 [North American, Canadian records, misidentification].

Type material.

Holotype. United States • ♂; Arizona, Cochise Co., Huachuca Mts., Miller Canyon; 31.4248, -110.26; 5,200' [1585 m]; 19.iii.1987; larva collected with Arbutus arizonica ; R. S. Wielgus leg.; emerged 24.v.1987 [reared by D.L. Wagner], DLW Lot: 87C4.5; Genitalia slide EvN4950; USNM01850751.

Paratypes (13♂, 6♀). United States - Arizona • 1♂; Cochise Co., Ash Canyon, Huachuca Mts.; 5100' [1550 m]; 6.x.1979; P.M. Jump leg.; Genitalia slide USNM16408; USNM01850740 • 1♂; Yavapai Co., 20 km W. Prescott, Yavapai CG [Campground]; 9.vi.1997; oak-juniper-pine; H.W. van der Wolf leg.; Genitalia slide EvN5492; RMNH.INS.25492. - California: 1♂ (abdomen missing); Contra Costa Co., Walnut Creek; 14.x.1961; J. Powell leg.; USNM01850749 • 1♂; Del Norte Co., Grassy Flat Campground, 3 mi. [4.8 km] W Patrick’s Creek; 2.x.1968; P.A. Opler leg.; at light; Genitalia slide USNM20961; USNM01850741 • 1♂; Lake Co., Pogie Point, Lake Pillsbury; 28-29.viii.1973; J. Powell leg.; at light; Genitalia slide DRD3151; USNM01850742 • 1♂; Los Angeles Co., San Gabriel Mts., San Gabriel Canyon, Red Box Canyon Road; 31.viii.1974; black lite; D.C. Frack leg.; USNM01850743 • 1♂; Madera Co., O’Neals; 26.iv.2015; V. + M. Albu leg.; Genitalia slide EvN4998; RMNH.INS.24998 • 1♂ (abdomen missing); Medocino Co., South of Piercy; 9.viii.1971, 10.viii.1971; R.H. Leuschner leg.; USNM01850750 • 1 ♂; same collecting data; EMEC752122 • 1♂; Riverside Co, San Jacinto Mts, Keen Camp; 4,500' [1370 m]; 31.viii.1974; D.C. Frack leg.; black lite; Genitalia slide USNM20877; USNM01850744 • 1♂; San Bernardino Co., Wild Horse Canyon, Rt. 2, 0.7 mi. [1.13 km] W Jct. Rt. 138; 4,800' [1465 m]; 21.vi.1974; D. Frack leg.; black lite; Genitalia slide DRD3403; USNM01850745 • 1♀; same collecting data; 23.vii.1975; Genitalia slide DRD3401; USNM01850746 • 1♂ [in ethanol]; San Diego Co., San Dieguito River Valley Conservancy, Site 1 (Volcan Mtn); 24.viii.2013; Joshua Kohn leg.; T, Upland, Malaise trap; Genitalia slide EvN4941; BIOUG08839-B12 • 2♀; Santa Barbara Co., 1 mi. NE San Marcos Pass; 1500' [460 m]; 7.vii.1965; J. Powell leg.; Genitalia slide USNM17493; EMEC1744182, EMEC1744183 • 1♀; Santa Barbara Co., 2 mi. [3.2 km] W Los Prietos; 7.ix.1969; P. Opler leg.; at light; Genitalia slide DRD3330; USNM01850747 • 1♀; Siskiyou Co., Happy Camp; 8.vii.1958; J. Powell leg.; at light; Genitalia slide DRD3329; USNM01850748 • 1♂; Siskiyou Co., 8 km SW Mount Shasta, Castle Lake; 12.viii.1992; H.W. van der Wolf leg.; Genitalia slide EvN4951; RMNH.INS.24951 • 1♀; Yuba Co., Marysville Buttes [Sutter Buttes]; 2.v.1928; H.H. Keifer leg.; CASENT8568092.

Non-type material examined, adults.

Canada - Ontario • 1♀; Ottawa, 40 km W, Almonte; 7.ix.1992; Kauri Mikkola leg.; alvar, ad lucem; Genitalia slide EvN4138; RMNH.INS.24138; MZH.

Non-type material examined, larvae.

United States - California • 9 larvae in ethanol; Marin Co., 400 Deer Valley Rd., San Rafael, Smith Ranch Homes; 15.iii.2017; S.J. Seybold, S. Swain leg.; ex collected stems and leaves, Marina strawberry tree, Arbutus × ‘Marina’ ( Arbutus unedo × A. andrachne ); RMNH.INS.31006, 31007, 31012-15 • 20 larvae (3-4th instar); same collection data; 11.iv.2017; S.J. Seybold leg.; ex collected stems and leaves Marina strawberry tree; CSCA • 2 larvae; same collection data; from native Arbutus menziesii ; RMNH.INS.31008, 31009 • 2 larvae on slide (barcoded); Sonoma Co., 2900 Wild Turkey Run, near intersection of Bennett Valley Road and Savannah Trail; 855 ft [260 m]; 15.iii.2017; S.J. Seybold, S. Swain leg.; ex collected stems and leaves, Arctostaphylos manzanita , Arctostaphylos spp. (broad leaf); slides RMNH.INS.31005.P, RMNH.INS.31010.P • 1 larva in ethanol; same collection data; RMNH.INS.31011 • 28 larvae in ethanol; same collection data; Marina strawberry tree, Arbutus × ‘Marina’, ( Arbutus unedo × A. andrachne ); RMNH • 6 larvae in ethanol; same collection data; from Arctostaphylos manzanita , Arctostaphylos spp.; RMNH • 4 larvae (1-2nd instar); 257 Perkins Street, Sonoma; 11.iv.2017; S.J. Seybold leg.; collected leaves Marina strawberry tree; CSCA.

Non-type material examined, leafmines.

possibly of E. thoraceleuca . United States - Washington • vacated mines; Washington, Chelan Co., Wenatchee National Forest, Entiat summit Road; 12.vii.2010; E.J. van Nieukerken leg.; EvN2010017; low Pinus ponderosa forest on ridge, leafmines on Arctostaphylos uva-ursi ; RMNH.INS.42859.

Additional online records - adults.

Canada - Ontario • 1♂, 1♀; Lambton Co., Port Franks; 21.viii.2021, 25.ix.2020; K. H. Stead leg.; BIOUG62319-H05, BIOUG74608-E04 (BOLD).

United States - Arizona • 1 adult; Cochise Co., Sierra Vista Southeast. Miller Canyon Upper Parking; 17.v.2022; Jim Eckert; https://www.inaturalist.org/observations/142023215. - California • 1 adult; San Diego Co., San Marcos; 31.vii.2018; Greg Smith leg.; https://bugguide.net/node/view/1568125 • 1 adult; Santa Clara Co., Silicon Valley, Stanford Academic Reserve; 5.vi.2021; Jen and Hilary Bayer leg.; Malaise trap; BIOUG92695-A02 (BOLD) • 1 adult; Tulare Co., Ash Mountain; 06.vii.2018; Graham Montgomery leg.; https://bugguide.net/node/view/1569217.

Additional online records - leafmines.

United States - California • Colusa Co., various localities; mines on Arctostaphylos manzanita ; 27.ii.2020, 4-5.ii.2021, 27, 28.iii.2021; K. Schneider leg.; https://www.inaturalist.org/observations/72384123, https://www.inaturalist.org/observations/72335843, https://www.inaturalist.org/observations/72447513, https://www.inaturalist.org/observations/39306497, https://www.inaturalist.org/observations/69086879, https://www.inaturalist.org/observations/69119629 • Contra Costa Co., Mount Diablo State Park; leafmines on Arctostaphylos manzanita subsp. laevigata ; 8.ii.2020; Ken-Ichi Ueda leg.; https://www.inaturalist.org/observations/38489869 • Los Angeles Co., Claremont, California Botanic Garden; 2 leafmines on Arctostaphylos insularis ; Steven Kurniawidjaja leg.; https://www.inaturalist.org/observations/150883693 • Los Angeles Co., La Cañada Flintridge, Descanco Gardens; 2 leafmines on Arbutus ; Steven Kurniawidjaja leg.; https://www.inaturalist.org/observations/155422286 • Marin Co., Santa Venetia, leafmine on unidentified host; 28.i.2020; Krissa Klein leg.; https://www.inaturalist.org/observations/38138633 • Modoc Co., FR-73, 0.1 road mi W Householder Reservoir entrance road; leafmines on Arctostaphylos manzanita ; 17.v.2021; K. Schneider leg.; https://www.inaturalist.org/observations/79232102, https://www.inaturalist.org/observations/79232103 • San Diego Co., 31.iii.2019; leafmines on Arctostaphylos rainbowensis ; James Bailey leg.; https://www.inaturalist.org/observations/21914712 • San Diego Co., Cleveland National Forest; 11.xi.2021; leafmines on Arctostaphylos ; Jorge Ayón leg.; https://www.inaturalist.org/observations/100888480.

Diagnosis.

Etainia thoraceleuca is easily recognized by the combination of a white thorax and the silver markings: a fascia and costal plus dorsal spot. Some Stigmella species have a similar pattern, but can be recognized by the distinct collar, comprising lamellar scales. Most similar are some species of Acalyptris , including the eastern A. thoracealbella (Chambers, 1873). This species has the pattern not so silvery, the antennae are paler, and the wings are narrower; moreover, the distribution does not seem to overlap much, but genitalia should be checked when in doubt. The male genitalia are characteristic of the genus Etainia by the valval apodemes, absent uncus, and structure of the phallus; it differs from E. ochrefasciella and E. sericopeza by the different shapes of the valva and gnathos, and the latter are very wide in E. sericopeza and very narrow in E. ochrefasciella . The female genitalia differ especially by the different structure of tergite 8.

Description.

Male (Figs 1 , 2 ). Forewing length 2.6-3.2 mm (2.9 ± 0.2, 7), wingspan 5.8-7.0 mm. Head: frontal tuft ferruginous, mixed with fuscous on frons, almost black on vertex, ferruginous in Canadian specimens, collar inconspicuous, comprising ferruginous or fuscous hair-scales. Scape and pedicel cream white. Flagellum fuscous, antenna with 49-57 segments (51.3 ± 2.9, 6), ratio to forewing length 16-19 (17.8 ± 1.4, 6) segments/mm. Thorax creamy white, tegulae either white or concolorous with forewing, forewing shining fuscous, pattern silvery white, consisting of a fascia at 1/3, and opposite costal and dorsal spots at 2/3, terminal fringe white beyond distinct fringe line, underside dark fuscous, no androconial scales present. Hindwing grey, a row of costal bristles behind frenulum, underside grey. Abdomen grey brown, genitalia with ochreous vestiture.

Female (Figs 3 , 4 ). Forewing length 2.6-3.4 mm (3.0 ± 0.3, 6), wingspan 5.9-7.8 mm. Antenna with 41-49 segments (43.5 ± 3.7, 6), ratio to forewing length 8-11 segments/mm. As male, but frontal tuft completely ferruginous in Canadian specimens. Hindwing with costal bristles.

Male genitalia (Figs 5 - 11 ). Capsule length 435-660 μm (544.0 ± 79.8, 6), 1.3-1.6 × as long as wide. Vinculum large, anteriorly truncate, posteriorly with U-shaped excavation. Tegumen produced into triangular, pointed pseuduncus, uncus absent. Gnathos with median lobe relatively broad at base, pointed at tip, length less than twice its width. Valva length 200-320 μm (255.9 ± 38.2, 6), relatively narrow, curved and tapering slightly to an abruptly down-curved apex; dorsal apodeme greatly elongate, sharply curved, and smooth; transtilla transverse bar straight, rather long, sublateral processes distinct, about half length of transverse bar. Phallus 325-460 μm (405.5 ± 49.0, 6), 2.9-3.4 × as long as wide; apically ending in a long tongue-shaped process dorsally, and a pair of ventral pointed carinae; vesica with the following sclerotizations: basally an H-shaped sclerotization, followed by a distinct striate cathrema and an indistinct complex sclerotized structure, ending in a single large pointed cornutus protruding from the phallus.

Female genitalia (Figs 12 - 17 ). Abdominal end broadly rounded, anal papillae a narrow band with more than 50 setae in total; T8 with pointed posterior margin; on T8 three transverse broken rows with groups of socketed setae, posteriorly two connected groups of ca 21-25 setae each; medially two widely separate groups of 12-13 setae at either side; anteriorly two groups of ca 14-17 setae. Anterior apophyses widely separate, with curved tips; posterior apophyses straight. T7 with medial indentation in posterior margin. Corpus bursae total length ca 710-855 μm. Ductus bursae with a paired sclerotized structure near cloaca and group of small spines laterally, more anteriorly; corpus bursae with paired elongate reticulate signa, usually different in length, longest 520-550 μm; ca 10-12 cells wide, shortest 360-425 μm, ca 10-17 cells wide. Ductus spermathecae with 2 indistinct convolutions.

Egg. In the few examples seen on leaf underside, the usual domed egg scale of Nepticulidae . When the mine develops, the egg is more or less in the center of the leaf spot.

Larva (Figs 18 - 40 , 45-52 ). First instar: head-capsule width 0.24 mm, length 0.27 mm, (overall length 2.78 mm) (n = 1), Second instar: head-capsule width 0.33-0.36 mm, length 0.35-0.37 mm, (overall length 4.21-4.59 mm) (n = 3); Third instar: Head-capsule width 0.47-0.48 mm, length 0.42-0.47 mm, (overall length 1.71-2.06 mm) (n = 6); Final (fourth) instar: head-capsule width 0.44-0.56 mm, length 0.41-0.53 mm, (overall length 2.63-4.71 mm) (n = 11).

Pupa (skin) (Figs 56 , 57 ). 2.2 mm long, 0.9 mm wide.

Cocoon (Figs 53 - 55 ). Yellow-brown and ovoid, 2.5-3.1 mm long and 1.5 mm wide. Emergence slit about half the length along the narrow periphery.

Biology.

Hostplants. Ericaceae : Arbutus arizonica (A. Gray) Sarg. (Arizona madrone), Arbutus menziesii Pursh (Pacific madrone), Arbutus x andrachnoides Link ‘Marina’, (Marina strawberry tree, possibly Arbutus unedo L. × A. andrachne L.), Arctostaphylos canescens Eastw. ( Eiseman 2022), Arctostaphylos ?glauca Lindl., Arctostaphylos insularis Greene & Parry (Island Arctostaphylos manzanita ), Arctostaphylos manzanita Parry (Manzanita), Arctostaphylos manzanita subsp. laevigata (Eastw.) Munz, Arctostaphylos pungens Kunth ( Eiseman 2022), Arctostaphylos rainbowensis J. E. Keeley & Massihi, most likely also Arctostaphylos uva-ursi (L.) Spreng. (Bearberry).

Life cycle. Eggs are apparently laid singly on the underside of leaves in late summer to early fall, where they remain quiescent for several weeks. In late fall, the larvae hatch and begin burrowing into leaf tissue. On the oviposition site there develops a red to black stained leaf spot; from there the larvae make a thin, linear mine running along the lateral and midveins of the hostplants’ leaves, often very straight or sometimes with a few loops; the frass line is central and almost completely fills the gallery; the mined area soon turns red to black. Larvae continue burrowing through the petiole and into subtending twigs where they mine phloem tissues. After feeding in the twig cambium for several months, larvae bore their way out of the twigs and drop into the leaf litter beneath the plant. The exit holes are little slits in the twig epidermis, resembling those of other nepticulids. On California’s north coast, this occurs from April to May. Larvae pupate in the duff, tying dead leaves and perhaps other organic material together with bright-saffron to orange silken cocoons. Pupation is complete by June with most adult moths emerging early to mid-May in 2019 and 2020. Moths were found between 26 April and 14 October, which may indicate two annual generations, or a rather irregular emergence of adults. Adults are usually found at light.

Damage details

(Figs 41-44 ). Initial damage symptoms appear as inconspicuous black spots on the hostplant leaf blade, caused by a larva tunneling in a wandering circular pattern (Fig. 41 ). The circles gradually enlarge until the larva encounters a lateral leaf vein. The larva then normally follows the lateral vein down to the midvein, through the petiole (Figs 41-44 ). Damage by the larvae can be seen on the undersides (and sometimes the top) of the leaf as a thin but conspicuous red to black line marking the tunnel. Sometimes a larva will follow the lateral vein to the edge of the leaf, and then circle toward the leaf center until it again finds a lateral vein. Once the larva reaches the thicker tissues of the petiole and begins boring into the twig’s cambial tissues the line gradually disappears. Twig bark excision with a scalpel will reveal substantial feeding damage in the cambium. Undamaged leaves of Arbutus normally last at least one season, sometimes a few months more ( Berner and Law 2016: table 2). All hostplants observed so far dropped their damaged leaves before the end of their first season.

As larvae from many leaves migrate into subtending twigs to feed, their numbers and associated damage become concentrated, damaging the cambium to such an extent that the distal portions of the twig are frequently killed. These branches wilt and die rapidly, leaving the wilted end of the twig to droop, shrivel, and then harden into a shepherd’s crook. Even when twigs are not killed, the bark splits and callus tissue will form on the twigs, disfiguring and sometimes distorting it. In severe cases, young Arbutus ‘Marina’ trees have been killed, and older trees rather severely disfigured, with less than 50% live canopy remaining. Damage to native Arctostaphylos manzanita and madrone does not appear to be as severe.

Parasitoids.

As might be expected for a moth in its native range, parasitoid wasp pupae have been found inside the mines on occasion. One Chalcidoidea parasitoid (most likely Eulophidae , Entedoninae , C. Eiseman pers. comm.) emerged in summer 2023 from cocoons from Sonoma (near Napa Co.) found by SVS on 11 May 2023; it made a circular exit hole on a broad cocoon surface (Fig. 53 ). A moth emerged from another cocoon from the same date and location during the same summer.

Distribution

(Figs 58 , 59 ). Most records are from California, where E. thoraceleuca has been found over much of the coastal ranges of California and collected from Del Norte County in the extreme northwestern part of the state to as far south as San Diego County, in adjacent Oregon (leafmines, Josephine Co., Rough and Ready Botanical Wayside, 42.0959, -123.6831; C. Eiseman pers. comm.), in Arizona in the Huachuca mountains (type locality), Chiricahua mountains (leafmines on A. pungens , Cochise Co., Cave Creek Canyon, Cathedral Vista Trail, 31.8866, -109.1721, C. Eiseman pers. comm.; illustrated by Eiseman 2022), Yavapai County, and three specimens from Ontario, Canada. Leafmines collected in Washington State also probably belong to this species.

DNA barcodes

(Fig. 60 ). We have DNA barcodes from eleven specimens, four larvae and seven adults: seven full barcodes belonging to BINBOLD:ACK1467 with an average KP2 distance of 0.39%, and a maximum distance of 0.83%, and three barcodes of the Canadian specimens belonging to BINBOLD:AEO1837 (no variation) at a distance of 1.5% to the nearest Californian sequence (Fig. 58 ). Unfortunately, we failed to amplify COI from the holotype.

The identical barcodes of adults and larvae undoubtedly show that the described larvae and damage belong to the same species as the adults.

Remarks.

The specimens from Canada differ in having a completely orange head and in their female genitalia; in both specimens the signa are almost equal length, 360 μm. In a Californian female specimen one of the three rows of setae on T8 seems to be missing. The genitalia of the male Canadian specimen could not yet be examined. For now, we consider the Canadian specimens as belonging to the same species, but further study and material is required to evaluate the possibility of hidden diversity.

Etymology.

The specific name, thoraceleuca, a noun in apposition, is derived from the Greek noun thorax (breastplate) and adjective leukos (white), referring to the characteristic white thorax.

Figures

Figure 60. Neighbor-joining tree of DNA barcodes (mt gene COI- 5 P) of Etainia species, using the Kimura distance model. Acalyptris scirpi (Braun, 1925) is used as outgroup. Labels show species name, Sample ID, life stage, Country, State or Province and BIN (Barcode Identification Number).

Figures 1 - 4. Etainia thoraceleuca, adult habitus 1 male Holotype AZ, genitalia slide EvN 4950 2 male, CA, Siskiyou Co., genitalia slide EvN 4951, RMNH. INS. 24951 3 female, CA, Santa Barbara Co., San Marcos Pass, 7. vii. / 1965 4 female, Canada, ON, Ottawa, genitalia slide EvN 4138. Scale bars: 1 mm.

Figures 5 - 8. Etainia thoraceleuca, male genitalia 5, 6 holotype, AZ, genitalia slide EvN 4950, respectively more ventrally and more dorsally focused 7, 8 CA, genitalia slide EvN 4951, capsule, focused at valval processes and separate detail of phallus. Scale bars: 100 µm.

Figures 9 - 12. Etainia thoraceleuca, genitalia 9, 10 male genitalia slide USNM 20877, phallus omitted, right valva illustrated separately, internal view 11 phallus, genitalia slide USNM 20961 12 female genitalia, genitalia slide USNM 17493. Scale bars: 0.5 mm.

Figures 13 - 17. Etainia thoraceleuca, female genitalia 13, 14 CA, genitalia slide DRD 3401, with detail of terminal segments, dorsally 15 CA, genitalia slide DRD 3329, detail signa 16, 17 ON, genitalia slide EvN 4138, with detail of signa. Scale bars: 200 µm (13, 16); 100 µm (14, 15, 17).

Figures 18 - 21. Larval whole body of Etainia thoraceleuca 18 first instar: a whole larva posterior (L) to anterior (R), dorsal view b close up head (ventral view) c close up posterior (dorsal view) 19 second instar (dorsal and ventral) 20 third instar (dorsal and ventral) 21 fourth instar (ventral-lateral).

Figures 29 - 40. Etainia thoraceleuca, larva, scanning electron microscopy [scale bars = µm] 29 early instar head ventro-lateral 30 early instar head ventral 31 early instar labium with spinneret, labial palps and maxillae with palps, ventral 32 mid instar dorsal spinneret and labial palps 33 mid instar dorsal spinneret 34 early instar spiracle A 4 35 mid instar A 8 - A 10 lateral 36 mid instar lateral A 10 37 mid instar A 8 - A 10 posterior lateral 38 early instar rows of spines in anal opening A 10 39 early instar ventral A 10 40 early instar lateral ventral A 10. Scale bars: 100 µm (30, 35 - 37); 50 µm (29, 31); 20 µm (32, 34, 38 - 40); 10 µm (33).

Figures 45 - 53. Active larvae of Etainia thoraceleuca boring in woody stems of Marina strawberry tree, Arbutus x ' Marina' from CA: Marin Co. unless otherwise mentioned 45 - 46 CA: Sonoma Co., S. Swain 47 - 50 open stem with larval head, dorsal view 51 larva in stem with anal rods visible 52 larva, removed from stem, attacked by a mirid nymph 53 Chalcidoid parasitoid, most likely Eulophidae: Entedoninae and cocoon of Etainia thoraceleuca with exit hole of parasitoid.

Figures 54 - 57. Cocoons (54 - 55) and pupal skin (56 - 57) of Etainia thoraceleuca.

Figures 41 - 44. Leafmine damage caused by Etainia thoraceleuca 41 Marin Co., CA: S. Swain, leafmine on Marina strawberry tree, Arbutus x ' Marina' 42 CA: Sonoma Co., S. Swain, leafmine on Arctostaphylos manzanita, Arctostaphylos spec. 43 CA: San Diego Co., S. J. Seybold, MA Siefker, coll., leafmine on Marina strawberry tree, Arbutus x ' Marina' 44 CA: Marin Co., S. J. Seybold, coll., mines on stems and leaves from Arctostaphylos manzanita, Arctostaphylos spec.

Figures 58 - 59. Distribution of Etainia thoraceleuca 58 in North America 59 in Oregon, California and Arizona.