Stigmella gallicola van Nieukerken & Nishida

van Nieukerken, Erik J., Doorenweerd, Camiel, Nishida, Kenji & Snyers, Chris, 2016, New taxa, including three new genera show uniqueness of Neotropical Nepticulidae (Lepidoptera), ZooKeys 628, pp. 1-63 : 6-12

Taxon classification Animalia Lepidoptera Nepticulidae

Stigmella gallicola van Nieukerken & Nishida sp. n.

Holotype male.

Costa Rica, Puntarenas province, Monteverde, Estación Biológica Monteverde, 10°19'06.9"N, 084°48'29.3"W, 1530 m, 26.x.2001 (adult emergence), col./rear: Kenji Nishida; host plant: Hampea appendiculata ( Malvaceae ), gall inducer on young leaf veins, pupate outside of the gall, cocoon spun 20.x.2001; RMNH Lepidoptera , Genitalia slide EvN3672, RMNH.INS.23672 (RMNH).

Differential diagnosis.

A large rather uniform moth, shining fuscous brown on almost all parts, with an orange frontal tuft and edged eye caps.

Description.

Male (Figs 1, 33). Head: frontal tuft orange; antenna with 33-34 segments (n=2); scape cream, with broad grey edge, flagellum brown. Thorax, forewings and hindwings, including fringe, fuscous brown, with strong reflections on forewing and thorax. Abdomen also fuscous, no anal tufts. Legs brown.

Female (Fig. 2). Antenna with 30 (n=2), ovipositor slightly protruding, otherwise as male.

Measurements. Male: forewing length 2.5 mm (HT), wingspan: 6.0 mm. Female: forewing length 2.5 mm (n=2), wingspan ca. 5.8 mm.

Male genitalia (Figs 9-13). Total length 265-300 µm. Vinculum anteriorly bilobed. Tegumen a narrow band. Uncus rectangular, posterior edge indented to almost straight, with many setae. Gnathos with two curved posterior processes, widely apart, transverse bar curved. Valva length 175-200 µm, more or less triangular, pointed tip slightly curved inward, inner margin serrate in middle, an inward pointed process on dorsal surface; transtilla with long straight transverse bar. Juxta almost triangular with tip anteriorly between valvae, ventrally two prominent setae. Phallus (Figs 12, 13) length 365-375 µm, flask shaped, widest at base, vesica with two large curved cornuti, 145-150 µm long (measured from base to tip in straight line) and several small denticulate cornuti.

Female genitalia (Figs 14-16). Total length of bursa ca. 1 mm. Ovipositor pointed (Fig. 14), anterior apophyses longer than posterior ones. T8 narrow, with ca. 18 long setae. Bursa covered with pectinations in a reticulate pattern, more prominently in caudal part (Fig. 15). Ductus spermathecae without convolutions, a circular spermathecal vesicle (Fig. 16).

Biology.

Host plant (Figs 19-20). Malvaceae : Hampea appendiculata (Donn.Sm.) Standl. A tree, occurring between Honduras and Panama from sea level to 1800 m on both the Caribbean and Pacific slopes in Costa Rica ( Fryxell 2007).

Gall (Figs 21-30). Galls were induced on leaf veins of young leaves and on axillary leaf buds. Galls on leaf veins are ovoid when mature and more swollen on the leaf underside; length 7-18 mm diameter 3-8 mm (n=18). Galls on axillary leaf buds ovoid by swelling of entire buds (Fig. 25) length 8.7- 11.2 mm, diameter 4.1-5.5 mm, gall base of ca. 1.6 mm diameter (n=5). Galls can cause deformation of young leaves. Gall chamber narrow, located longitudinally in central part of gall, and line with compacted dark brown frass on lower part of chamber, part of the frass reaching towards nectary gland (Figs 26, 27). Galls were found on ca. 2 meter-tall treelets or large trees of 8-25 m (n=7), however we were unable to examine higher parts of large trees. Most of the collected galls were empty, having a more or less rectangular-shaped exit slit of less than 1 mm wide (Fig. 30). We found inquiline phorid fly larvae ( Diptera : Phoridae ) inhabiting old gall chambers. The gall was already recorded by Hanson et al. (2014).

Egg. Egg position unknown. Probably laid near or at foliar nectaries (nectar glands) abaxially on primary veins of leaf buds or very young leaves.

Larva (Figs 28, 29, 32). Early to late instar translucent (n=7), mature last instar translucent yellowish green, 6.0 mm long (n=1).

Cocoon (Fig. 31). Pale brown to brown, oval, exit slit side is broad and opposite side tapered (apple seed-shaped), 2.8-3.2 mm long, 1.7-1.9 mm wide (n=2). Under rearing conditions inside plastic bags, cocoons were constructed on either host leaf surface or on paper towels (n=5). Under natural conditions in the field, no cocoons were found on host plant leaves or stems near the galls.

Voltinism and habits. Larvae were found inside the galls in March, May and June. Adult emergence has been recorded in January, April, May, June and October.

Parasitoids . Braconidae : Adelinae: Adelius sp., endo-parasitoid, koinobiont of host larva and pupating inside host cocoon. It was reared from the Alto Masis Station site (n=2). Adelinae are specialised parasitoids of Nepticulidae ( Yu et al. 2011).

Distribution.

Costa Rica: Alajuela, Heredia and Puntarenas provinces. Galls have been recorded mostly from Caribbean/Atlantic slope in lowland Costa Rica. The type locality is near the continental divide on the Pacific slope.

DNA barcode.

The Holotype (RMNH.INS.23672) and one female (RMNH.INS.23739) are barcoded, with less than 1% difference. Barcode Identification Number BOLD:ACG9386. The female was also sequenced for other genes and used in the molecular phylogeny ( Doorenweerd et al. 2016). Sequences may be retrieved in BOLD and Genbank under voucher/sample ID RMNH.INS.23739.

Remarks.

The genitalia of Stigmella gallicola resemble somewhat those of the Stigmella betulicola group, but in our multi-gene molecular analysis it groups in the clade which contains the Stigmella prunifoliella and Stigmella ultima groups, without a strongly supported position.

There are only few cases of galling in Nepticulidae known, and this species is the first known in the genus Stigmella . Galling has evolved independently several times in Nepticulidae : the North American Ectoedemia populella Busck, 1907 makes a petiole gall ( Busck 1907; Wilkinson and Scoble 1979), but starts with a short leafmine along the midrib. Its behaviour caused Busck to name the new (then monotypic) genus Ectoedemia (= making an external swelling), but only a few species feeding on Populus have similar habits and all other species in the genus are leafminers. The European Trifurcula pallidella (Duponchel, 1843) makes a spindle shaped gall in the stem of Cytisus species ( Fabaceae ) ( van Nieukerken et al. 2004), but this gall growth appears to be caused by the intense mining activity in a small portion of the stem. Muhabettana nigrifasciata (Walsingham, 1908) of the Canary Islands starts with a small gall on a vein, and later the larva makes a long leafmine in the leaf of Periploca laevigata ( Apocynaceae ) ( Klimesch 1972); Klimesch uses the German word “Gallenmine”. Ectoedemia castaneae ( Busck 1913) was according to Busck reared from small galls on young twigs, but this is probably not a real gall-former, but an effect of a spiral barkmine in a thin branch: the species is synonymised with the barkminer Zimmermannia bosquella (Chambers, 1878) ( van Nieukerken et al. 2016). Of all these species, Stigmella gallicola induces and forms the most conspicuous swellings, and its biology is adapted to live inside the gall chamber. Gall-forming nepticulids could have been overlooked, and further studies in gall-inducing Lepidoptera may reveal more species. It is worth mentioning that larvae of Rhodoneura cf. terminalis (Walker, 1865) ( Thyrididae ) induce spindle-shaped galls on the stem apex of Hampea appendiculata . They were reared at Estación Biológica Monteverde and OTS La Selva Biological Station (K. Nishida, personal observation).

Etymology.

The specific name is a noun in apposition, derived from the Latin noun galla (= gall) and suffix -cola, "dweller in".

Other material examined.

6♂, 3♀, 5 adults, galls, larvae. Costa Rica: 1♂, Heredia Province, Puerto Viejo de Sarapiquí, Trimbina Biological Reserve, 10°24'59.81"N, 084°7'27.82"W, 161 m, gall inducer on young leaf veins of Hampea appendiculata , adult emergence18.i.2003, Kenji Nishida, Genitalia slide JCK15024; 2♀, Heredia Province, Puerto Viejo de Sarapiquí, OTS La Selva Station, main bridge, 10°25'53.42"N, 084°0'13.22"W, 50 m, gall inducer on young leaf veins of Hampea appendiculata , e.l. 2-5.v.2002, Kenji Nishida, Genitalia slide EvN3739, RMNH.INS.23739; 1♂, Alajuela Province, Parque Nacional Volcán Tenorio, Alto Masis Station, 10°36'39.99"N, 085°0'1.59"W, 955 m, gall maker on Hampea appendiculata , young leaf veins, adult emergence 20.vi.2007, Kenji Nishida; 4♂, 1 ♀, Puntarenas Province: Monteverde, Estación Biológica Monteverde, 10°19'06.9"N, 084°48'29.3"W, 1530m, gall inducer on young leaf veins of Hampea appendiculata , adult emergence 17. iii– 10.iv.2015, cocoons spun approx. 20.iii.2015, Kenji Nishida (RMNH, MZUCR).

More data from BOLD

[specimen not examined, same BIN]. 1 adult, Costa Rica, Guanacaste, Area de Conservacion Guanacaste, Sector San Cristobal, Estacion San Gerardo, 10.88 -85.389, 575 m, 17-24.ii.2014, DH Janzen, W Hallwachs, Malaise trap GMP#05845, laguna, BIOUG24701-G07 (BIOUG).