Erechthias grayi, Davis, Donald R. & Mendel, Howard, 2013

Davis, Donald R. & Mendel, Howard, 2013, The genus Erechthias Meyrick of Ascension Island, including discovery of a new brachypterous species (Lepidoptera, Tineidae), ZooKeys 341, pp. 1-20 : 9-12

Erechthias grayi sp. n. Figs 7-10, 18, 28-31

Diagnosis.

Adult (Figs 7, 8). Head: Scales generally slender with bidentate apices; scales of frons smooth, appressed, directed dorsad, pale brown to gray on lower frons becoming dull white to pale gray at top of frons; scales of vertex erect or mostly so, especially over occipital tufts, fuscous, some with grayish white apices. Labial palpus with scales flattened and appressed dorsally, mostly dark grayish brown with scattered paler scales; venter of second segment with a dark brush of long, slender, erect scales and a lateral series of ~ 6-8 long, dark bristles; 1-2 bristles also arising laterally from basal segment. Maxillary palpus elongate, 5-segmented, approximately as long as labial palpus. Antenna ~ 1.6 × the length of forewing; scales smoothly appressed, dark fuscous; scales of scape and pedicel moderately broad; flagellum without cilia and with a single row of more slender scales completely encircling each segment.

Thorax: Forewing brachypterous (Fig. 18), length 1.4-1.8 mm. Dorsum of thorax dark fuscous dorsally, with a few dull white scales at caudal margins of tegula and mesonotum; mostly grayish white ventrally. Forewing similar to dorsum in color, dark fuscous with an irregular scattering of dull white scales at base of wing and mostly crossing wing beyond middle; a slightly larger concentration of dull white scales at apex and extending a short distance along costa; fringe almost completely lacking, restricted to apex. Hindwing minute (Fig. 18), slightly variable in size, without scales; length ~ 0.15 mm; a single stout frenulum present in male ~ equal to length of hindwing (frenulum not examined in female); fringe absent. Fore and midlegs fuscous, lightly irrorated with pale grayish white scales; apices of tibia and tarsomeres ringed with grayish white; hindleg generally paler in color.

Abdomen: Dark fuscous dorsally, mostly grayish white ventrally. Eighth segment without coremata.

Male genitalia (Figs 28, 29): Segment 10 mostly membranous; uncus lobes indistinct, broadly rounded. Tegumen consisting of a relatively narrow dorsal ring. Vinculum broad, V-shaped, gradually tapering anteriorly with an acute anterior apex; vinculum ~ 0.7 × the length of valva. Valva simple; cucullus broadly triangular with narrowly rounded apex; costal margin densely setose. Juxta well developed as an elongate U-shaped pouch. Aedeagus slender, ~ 1.3 × length of valva; vesica with numerous, minute, spicular cornuti; base of aedeagus moderately flared, not divided.

Female genitalia (Figs 30, 31): Eighth sternite weakly sclerotized; ostium opening near anterior margin; an irregular cluster of ~ 5 pairs of long setae encircling caudal margin of eighth segment. Antrum slender, length ~ 3 × maximum width. Ductus bursae slender, elongate, slightly longer than anterior apophysis, gradually enlarging to moderately large, ovate corpus bursae; walls of corpus bursae membranous except for very small, elongate signum; distal, more slender half of signum projecting beyond wall of corpus bursae.

Etymology.

The species name is a patronym for Alan Gray, a botanist who assisted Howard Mendel with the collection of this species on Ascension Island.

Holotype.

♂, ASCENSION ISLAND: Green Mountain, 743 m, Elliot’s Path, (Windy Corner), GPS 7.57S, 14.21W: 6 Aug. 2003, H. Mendel, BMNH(E) 2003-137, digital image captured (BMNH).

Paratypes.

ASCENSION ISLAND: same locality as holotype: 11 ♂, 1 ♀, 13 Dec. 2005, H. Mendel, BMNH slide 33642 ♀, BMNH(E) 2006-13; 4 ♂, 21 Nov. 2012, H. Mendel and A. Gray, USNM slide 34532 ♂. ASCENSION ISLAND: White Horse Hill [Little White Hill], S. E. Bay: 2 ♂, 23 Aug. 2012; [pitfall trap]; Ms L. White, USNM slide 34533 ♂. White Horse Rock [Little White Hill, S. E. Bay]: 2 ♂, 29 May 2013; running over lichen covered rock; pooter; leg. A. Wakeham-Dawson; digital image captured. (BMNH, USNM).

Distribution

(Fig. 1). Ascension Island. Erechthias grayi was at first thought to be confined to the higher elevations of Green Mountain where it was found on several occasions at altitudes around 743 m, in a very moist area frequently shrouded in cloud. Recent captures at Little White Hill, an extremely arid area at altitudes below 200 m show that Erechthias grayi is tolerant of a wide range of conditions. What the two areas do have in common is that the vegetation and habitat are comparatively undisturbed. Probably, Erechthias grayi would have been more widespread on Ascension prior to human habitation and the disturbances accompanying human settlement.

Biology.

Becauseadults have been collected in close association with lichen covered rocks, it is likely the larvae are lichenivorous, a frequently used food source in this group of moths. Several (13) small (3.5-4.2 mm long) mature larval cases, some with pupal exuviae attached (Figs 9, 10), were collected under lichen covered rocks at White Horse Hill, on the same day that an adult was collected there by A. Wakeham-Dawson. It is likely that these are the larval cases of Erechthias grayi , but larval rearings will need to be conducted to confirm this. The cases are mostly white, speckled with small grains of sand and minute, dark fragments from the rocky substrate.

The behavior of the moths in the field was unusual. They would cling firmly to the bare rock, lichens (Fig. 3), and small plants in exposed situations and were only seen to move when disturbed, and then reluctantly. They would hop a few inches in a very bug-like ( Heteroptera ) manner and were most easily collected using an aspirator (pooter). Wakeham-Dawson (see paratype data) observed adults running over a lichen covered rock at White Horse Hill.

Remarks.

Erechthias grayi is the only species within this large genus known to possess brachypterous adults, and thus is the most distinctive moth within Erechthias . The male and female genitalia of Erechthias grayi are most similar to those of Erechthias darwini Robinson (1983), one of the few species of Lepidoptera known to inhabit St. Paul’s Rocks (Pedro e Săo Paulo, Fig. 1), located slightly over 1000 miles northeast of Ascension Island. The male saccus of Erechthias grayi is more triangular and the female signum is more slender than those of Erechthias darwini . Most significantly, the adults of Erechthias darwini (Fig. 11) are fully winged and capable of flight. However, considering their genitalic similarities and geographical proximity, it is possible that grayi may have shared relatively recent common ancestrywith darwini.

Reportedly, some form of wing reduction has occurred in either 25 ( Sattler 1991) or as many as 35 families ( Heppner 1991) of Lepidoptera . The two family totals quoted probably differ because Sattler did not include species displaying only slight wing dimorphism, and also because of some differences in the family classification followed by each author. Because of rather obvious reasons involving different selective pressures and flight requirements that exist between the sexes, wing reduction has rarely evolved in male Lepidoptera . Most species that have developed wing reduction in both sexes occur on small oceanic islands or in restricted coastal habitats ( Sattler 1991, Heppner 1991, 2010, Wagner and Liebherr 1992). Although several ecological and environmental factors can lead to a loss of flight among insects, the effect of continuous strong winds such as occur on isolated islands have long been considered a primary reason for wing reductions, particularly in Lepidoptera males ( Sattler 1991, Wagner and Liebherr 1992). Previously, eight species representing five genera of Tineidae had been reported to exhibit some form of wing reduction, with four species (including three species of Pringleophaga Enderlein and one of Proerodesma Meyrick) being brachypterous in both sexes ( Sattler 1991). No member of the large genus Erechthias had been reported as brachypterous prior to this report.