Poplar Fly Unrecorded in Britain

POPLAR FLY UNRECORDED IN BRITAIN.

143

POPLAR FLY UNRECORDED IN BRITAIN. B Y THE H O N .

SECRETARY.

THE River Dove rises at Denters Hill in Mendlesham, and runs north through Eye to fall into the Waveney at Hoxne. In Thorndon parish it receives at Cats Bridge a small tributary that rises near Plash-farm in Bedingfield, and this formerly splayed into Thorndon Fen, a broad and mile-long sheet of water immediately east of Cats Bridge. Unfortunately the area is rapidly drying : dull cattle-marshes exist where, so lately as a score of years ago, I well remember shoulder-high Hemp Agrimony and Angelica sylvestris flowers to have been profuse. Actual water is reduced to the sluggish stream, some ten feet broad by one foot deep this droughty summer when Alluvium from Chalky Boulder Clay was new-dug out, which will further dessiccate the Fen's humidity ; though still parts are so boggy as to show vast stretches of Reeds, Meadow Sweet and Tlialictrum flavum, too coarse to be worth haycutting. To the zoologist this Fen is virgin ground, excepting a half-dozen visits accorded it by our Member the Revd. H. A. Harris and me during 1924-6, when nothing of note occurred but many of the Fossor Hoplisus 4-fasciatus, Fab. and one or two Clearwings, Algeria vespiformis, L., on Angelica flowers. Belligerently restricted transit caused me to work the place again this summer from 22 June, when the Broads' hoverer-fly Tropidia scita, Harr., was profuse among Yellow Rattie.

In one corner of a swampy meadow and a couple of feet above fen-level, a tall Black Poplar tree had blown down last year and was now lying semi-prone, sound-barked and still sprouting leaves, with its top six feet from the ground. This trunk I was searching in hot sun and SW. breeze on 5 July, when its waving wings drew my attention to a Velvet Flv that was slowly Walking along the exaet ridge of bark : presumably a kind of Trypetidce, and certainly quite new in my own experience. Leaves rendered a net useless, so I tried to box him, but he flashed away laterally and downwards along the trunk's bevelled side before the box even approached him.

I waited, knowing how often such Flies will return, and in a couple of minutes saw him (though nothing of his return) on that same spot again, when a glass-topped box was slammed over him at 100 m.p.h. ! But protracted search produced no more. Dull showery weather deferred a second visit tili 14 July, when two more were similarly taken (both at third attempt) on that trunk ; though on 15th all but one were missed. This was a solitary Populus nigra, L. ; a quarter-mile away a half-dozen old and much decayed Poplars, the sole ones in sight, rose sheer from a ditch-side in the wettest part of the Fen ; on their live vertical trunks and barked fallen branches more speeimens were found in light SE. wind of 17th. By 19th the species' heyday seemed attained, for nearly a dozen were observed at the two sites. Our Member,

144

POPLAR FLY UNRECORDED I N BRITAIN.

Dr. Hocken, boxed one of the five we saw in light E. air on 20th ; and in stiff S. breeze on 26 July another specimen was in my net, after it had been blindly swept over the vertical bark : a not unprofitable method of collecting Diptera. Few showed in the NE. wind of 3rd, but on 6 August a large live Poplar branch had just blown down, upon whose smaller branches the oculatissimus Mr. Jim Burton and I counted fully a score in sun and stiff WNW. breeze.

Thence its numbers diminished tili, in the small south air of 19th, only three gravid females were observable. Hence their English season appears co-extensive with the month of July and half August in place of the recorded Continental June and July.

The black and grey velvet body, with banded wings, renders this Poplar Fly practically invisible upon the variegated grey bark {bearing patches of Lichens, which Mr. Mayfield names Physcta stellaris, Nyl., Xanthoria lychnea and Parmelia fuliginosa var.

Icetevireiis, Nyl.) until it moves, when the Walking legs seem muscularly to control the swaying of the wings. All were seen within an hour of noon and in sunshine, though they appeared unaffected by its momentary withdrawal. When on horizontal surfaces they never leave the highest point, but march slowly along the exact ridge. None were observed in flight, excepting when frightened from their fulcrum and then the eye was unable to follow them more than a few inches. Shelter is certainly sougbt at dusk as several, kept in boxes alive over night, rested in the darkest spots before sundown. Oviposition was not witnessed ; in hot sun, they would nestle into bark-crevices and there lie still as though basking ; but they never sought safety by such retirement. The ovipositor is of two segments, the basal black and apical dull flavous ; latter is a parallel-sided tube, longer than broad and as long as apical tergite, flat and centrally sulcate throughout, apically truncate, extruding to nearly its own length atrans-striate and apically acuminate spicula : the two segments combined are fully half the abdominal length.

The sole Insects present that might be directly associated are : Nymphs and imagines of the Bug Xylocoris ater, Duff., by sucking larvae ; females of the Ichneumon Omorga difformis, Gmel., by internal parasitism ; and the nesting Aculeates Pemphredon lugubris, Ltr., Crabro vagus, L. and Megachile Willughbiella, Kirby.

Indirectly associated are : the Sawflies Emphytus togatus, Pz. et carpini, Fall., the Diptera Mosina albipes, Fall.,Lonchea cliorea, Fb. and Sapromyza longipennis, Fb., all sitting on Poplar leaves ; on the bark were such Flies as various Medeteri, Xylota floruvi, Fb., large and small Sarcophaga, Nyctia halterata, Pz., Stomoxys calcitrans, L., Morcllia hortorum, Fall., Anthomyia pluvialis, L., Eustalomyia liilaris, Fall.* and Phorbia ; Aying at and sitting on * \n EGG, laid by E. hilaris, is at first pure white, subcylindrical but slightly convex on the under (as extruded f r o m ovipbsitor) surface, with extremities rather obtuse ; dulled by its surface being mmutely and confluently punctate ; length 1 m m .

POPLAR FLY UNRECORDED IN BRITA1N.

145

the trunks vvere : Rhagio scolopaceus, L., Anisopus punctatus, Fb. and numerous Gnophomyia lugubris, Zett., of which last one was ovipositing in hot sun on 19 July between bark-chinks on top and dryest part of trunk. The Fly with most similar habits, however, is the very local Xylomyia marginata, Mg. (Trans, v. 115), which occurred sparsely, with VerralT's füll ränge of 5-7£ mm., on the bark or Aying about it throughout the above six weeks.

As I knew Mr. H. W. Andrews was working on Trypetidae, I sent him the Poplar Fly to which he was at once able to give the name M I E N N I S OCTOPUNCTATA, Coq. The species was first described by M. A. I. Coquebert in 1798 (Bull. Soc. Sei. Philom.

Paris xix, p. 145) and in the 1804 part of his " Illustratio Iconographica Insectorum," p. 110, pl. xxiv, fig. 17 : it was considered a Trypeta by Meigen and Ortalis by Macquart, but the new genus Myennis (sie) was erected for it in 1869 by Rondani. Seguy's Muscides Acalypteres transfers Miennis at p. 46 to the saprophagous family Pterocallidce, which also is new to Britain and differs from Ortalidce in having the subcostal vein peculiarly strong, third basal cell acuminate on anal vein, and in lacking antennal fossae, sec.

Lindner's 1924-32 Die Fliegen der Palaearkteschen Region. I prefer to follow Hendel (Gen. Ins. et Deut. Ent. Zeit, 1909) in considering Pterocullinee as a subfamily, mainlv neotropic, of Otitida (as priority shows we must term the old Ortalidce, sec.

Hering).—I have slightly elaborated Seguy's French description of M. 8-punctata :— Body black, covered in parts by dense grey pruinosity. Head in front, and on the interocular area, red ; antennal fossae wanting.

Antennae testaeeous, subinfuscate above; arista black. Mesonotum bearing two margo-discales bands, anteriorly of pieeous pruinosity, posteriorly of nitidulous black as also is the Scutellum, of which the apex is always red-marked, often produced to its base ; two supra-alar setae strong, one weak sternopleural, propleural wanting. Abdomen with dorsal third segment apically pieeous, fourth nitidulous black bearing central dull and pieeous triangle, fifth and sixth apically nitidulous. Legs testaeeous, basally black ; femora except apices, and three-four apical tarsal joints, infuscate.

Wings hyaline, decorated with three oblique pieeo-flavidous fasciae that are attenues en arriere ; alar apex, and small subcircular costal spot before it, black ; subcostal vein incrassate towards its apex. Length, 3-4 mm.—Its ill-known distribution seems to be from Syria, where its larvae have been considered a pest upon Melons, through central Europe, Austria where it is locally common on tree-trunks and planks in fields (Schiner) and France (Meigen), as far from Amiens in the north as Hautes Pyrenees in the south, where Pandelle noticed it Walking, with wings balanced like Sepsis though I should have rather said Toxoneura, at Tarbes in June and July on barked Poplars (whereon Du Buysson found it also in Allier) and the fungoid bark of fallen trees.

146

POPLAR FLY UNRECORDED IN BRITAIN.

[Since writing the above account, I have found that the name and not the Insect is new to Britain. Verrall, in both his 1888 & 1901 British Lists, enters Loxodesma palustris, Mg. (now to be deleted as British), under which erroneous title he misidentified the present species. Prof. Martin Hering records it, ut dicetur, under its correct name, in his Continental work from the fens of Upware in Cambs on the strength of a pair, now Over a half-century old, still in the Verrall collection at Newmarket in Suffolk.—C. M.]

SAWFLIES OF 1944.—Any collector, beginning this year to work the Tenthedinidae, would be all too prone to consider our County a terribly poor place for them, since never have I experienced a greater dearth here. Not only were individuals, with the usual exceptions of such things as Athalia lineolata, Lep., frequently observed in cop. during August and Allantus arcuatus, Fst., first seen 11 May on Brandeston kingcups, sparse but only three kinds of note appeared the entire season. Cephus pygmceus, L., unusually rare, first emerged on 23 May ; and a $ Janus cynosbati, Fab., a novelty to the parish, was running on Monks Soham downstairs window 1 June. Xyphydria prolongata, Geoff. : rare in July at Thorndon Fen and on 17th a $ of 17 mm. in sun at 3 p.m. was biting with jaws a hole in bark of new-felled Willow post in Cretingham marshes. Several Arge ustulata, L., were in Monks Soham päd dock on 2 June ; and of A. ciliaris, L. (NEW to Suffolk ; add at Trans, iii, p. 19), a half-dozen of both sexes occurred on Heracleum fiowers at edge of Thorndon Fen (Btn) and those of Angelica at Brandeston, 20 July to 11 August. On Angelica at the last was also Hemichroa crocea, Geoff. on 24 August. Holconeme crassa, Fall., was swept there on 20 May ; Pristiphora crassicornis, Htg., in Thelnetham Fen 30 April ; and Eriocampoides variipes, Klg., from Poplar at Cretingham 17 August. Larvae of Rhadinocercsa micans, Klg., defoliated Ires in Thorndon Fen (cp. p. 58 supra).

The first Q Strongylogaster cingulatus, Fab., was on Knettishall Heath by 25 June ; StEmphytus calceatus, Klg., in Thelnetham and Brandeston marshes, in the former of which one Dolerus anthracinus Klg., was netted and many Rliogogasterfulvipes, Scp., seen 30 April.

Tenthredo colon, Klg. (NEW to Suffolk : add at I r a n s , iii, p. 28), was sitting in small numbers on marsh herbage by the R. Deben at Brandeston during 11-17 August; there they looked and behaved so like T. livida that I should have passed them for that common species, if the date had not occurred to my mind.—CLAUDE M O R L E Y .

AN

UNRECORDED

BRITISH

FLY :

MIENNIS

8-PUNCTATA

(p.

145).