Glyphuroplata pluto (Newman)

(Figs. 10, 50–52, 134)

Reared specimens. CONNECTICUT: Hartford Co., Granby, East Barndoor Hill, 20.vii.2019, em. 23–29.vii.2019, C.S. Eiseman, ex Digitaria ischaemum, # CSE5723 (4 adults, MLBM); Litchfield Co., Salisbury, Mt. Frissell, 12.vii.2022, em. 21.vii.2022, C.S. Eiseman, ex Dichanthelium acuminatum ssp. fasciculatum, # CSE7647 (1 adult, MLBM) ; MASSACHUSETTS: Franklin Co., Northfield, 42.647288, -72.424999, 17.vi.2020, em. 26.vi.2020, C.S. Eiseman, ex Dichanthelium clandestinum, # CSE6304 (1 adult, MLBM); Notch Mountain (42.700612, -72.430843), 8.vi.2019, em. 24.vi.2019, C.S. Eiseman, ex Dichanthelium acuminatum ssp. fasciculatum, # CSE5358 (1 adult, MLBM) ; NORTH CAROLINA: Durham Co., Durham, Pelham Rd., 29.vii.2017, em. by 10.viii.2017, T. S. Feldman, ex Digitaria, # CSE4099 (1 adult, ZFMK); Scotland Co., Laurinburg, St. Andrews University, 3.ix.2015, em. by 14.ix.2015, T.S. Feldman, ex Digitaria ciliaris, # CSE2111 (1 adult, MLBM); 31.viii.2016, em. 4.ix.2016, T.S. Feldman, ex Digitaria ciliaris, # CSE2970 (1 adult, MLBM); 15.ix.2016, em. 16.ix.2016, T.S. Feldman, ex Digitaria ciliaris, # CSE3004 (1 adult, MLBM); 17.x.2016, em. by 6.iv.2017, T.S. Feldman, ex Digitaria ciliaris, # CSE3400 (1 adult, ZFMK) ; OKLAHOMA: Payne Co., Mehan, 36.014339° N, - 96.996744° W, 1.vi.2018, em. 14.vi.2018, M.W. Palmer, ex Digitaria, # CSE4619 (1 adult, MLBM) ; RHODE ISLAND: Washington Co., Charlestown, Carter Preserve, 41.433219, -71.688155, 2.vii.2020, em. 7.vii.2020, C.S. Eiseman & J.A. Blyth, ex Dichanthelium dichotomum ssp. microcarpon, # CSE6357 (1 adult, MLBM) .

Other collected mines. MASSACHUSETTS: Franklin Co., Northfield, 276 Old Wendell Rd., 8.viii.2019, J.A. Blyth & C.S. Eiseman, Digitaria sanguinalis (iNat 203130620); Worcester Co., Southbridge, 22.vi.2016, Dichanthelium dichotomum (iNat 203130244); NORTH CAROLINA: Scotland Co., Laurinburg, St. Andrews University, 10.ix.2015, T.S. Feldman, Digitaria ciliaris .

Hosts. Poaceae: * Dichanthelium clandestinum (L.) Gould, D. dichotomum (L.) Gould, D. lanuginosum (Elliott) Gould (= D.acuminatum ssp. fasciculatum (Torr.) Freckmann &Lelong), D. microcarpon (Muhl.ex Elliott)Mohlenbr. (= D. dichotomum ssp. microcarpon (Muhl. ex Elliott) Freckmann & Lelong), * Digitaria ciliaris (Retz.) Koeler, D. ischaemum (Schreb.) Muhl., D. sanguinalis (L.) Scop., Panicum capillare L. (Frost 1924). The record of Panicum from Eiseman (2014) is uncertain; the plant was a seedling of an undetermined grass with hairy leaves, and it was presumed to be a Panicum based on Frost’s (1924) record from P. capillare, but we have never found leaf mines on a confirmed Panicum . Upon reexamining photos of the plant, we find that it is consistent with Dichanthelium lanuginosum and not with Panicum capillare . Staines (2015) additionally listed Andropogon gerardii Vitman; this is based on a specimen label from Iowa that reads “from B. Blue stem” (Riley 1985). The label likely does refer to A. gerardii, which is known as “big bluestem”, but whether the specimen was reared is unclear.

Biology. The only previous description of a Glyphuroplata pluto mine is that of Eiseman (2014), who reported a full-depth blotch mine with frass in long, crisscrossing strands, in what was thought to be a Panicum seedling. No egg was found. In subsequent observations we have continued to have difficulty in finding the egg, but it was found in one mine on Digitaria ciliaris and one on D. ischaemum . In each case the egg was embedded in the upper leaf surface 10–15 mm from the apex, beneath what appeared to be a flap of leaf epidermis (Fig. 10). We have observed larvae mining in small leaves to enter a second leaf to complete development, and this habit combined with the concealment of the egg accounts for the difficulty in locating it. The larvae are bright yellow in contrast with the whitish larvae of most hispines we have reared. Although all other G. pluto mines we have seen have matched the description and illustration in Eiseman (2014) (Figs. 50, 52), those on D. ciliaris are rather different, having a characteristic patchy appearance—particularly when viewed from the lower leaf surface—due to having some patches that are full-depth and some where the mining is confined to the upper mesophyll (Fig. 51). The frass in these mines is mostly in very short fragments rather than the usual long strands. One completed mine was 8 cm long and varied from 2 to 6 mm wide.

Parasitoids. Nine adults of Baryscapus Förster ( Eulophidae) emerged by 7 September 2015 from a single Glyphuroplata pluto larva mining a leaf of Digitaria ciliaris collected on 3 September (CSE2112, BMNH). A larva collected on 10 September yielded eight Baryscapus and one Pnigalio Schrank (CSE2110, BMNH). The mine on Dichanthelium dichotomum produced a single Pnigalio (CSE2700, BMNH), and the Connecticut collection from D. lanuginosum produced a Hemiptarsenus Westwood ( Eulophidae) (CSE7646, CNC / iNat 203132119). No parasitoids have previously been reported from any species of Glyphuroplata .

Notes. In New England we have often found this species mining leaves of young grasses that are not yet in flower and are thus not identifiable. We determined one Dichanthelium species by returning later in the season to the patch from which it had been collected; the Digitaria species from Connecticut and Massachusetts were determined by uprooting the host material and growing the plants in pots until they flowered in mid-August.

Our barcoded specimens of G. pluto belong to BIN BOLD:ADO8104.