Náttúrufræðingurinn - 1965, Page 58

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NÁTTÚRIJFRÆÐINGURINN
It has been suggested (Oliver 1962) that D. ursus might be a synonym of
D. hyperborea Holmgren but this still requires further study. Neither ur.sus
nor hyperborea has been found in mainiand Iceland. It is possible that
Edwards’ association of the sexes is incorrect as the specimens in Peterson’s
collection were captured witli males of D. zeryni Edwards. Tltis is the first
record of D. zeryni in Iceland. Also it is possible that more than one northern
Diamesa have females with large, yellowish cerci. Although the Surtsey speci-
men is consiclered here to be what Edwards (1922) interpreted as 1). ursus,
confirmation must await a complete revision of the systematics ol Diamesa.
A descriptjon of the fetnale of Diamesa ursus from Surtsey
The specimen is mounted on a slide and deposited in the Museum ot Natural
History, Reykjavík.
Antenna. — Pedicel with 1 ventro-lateral bristle. Flagellum with 7 segments,
all distinctly separated; terminal segment about equal to combined lengths of
preceding three segments, with weak sub-terminal bristle.
Head. — Eye hairy. Bristles on dorsal part of tempora extending to cover
most of dorso-anterior part of vertex, not reaching mid-line of vertex. Clypeus
rectangular in anterior view, sparsely covered with bristles except on dorsal
fifth. Palp with 4 segments, segment 2 swollen distally with prominent round
sensory organ.
'I'liorax. — Dorsal-central lirislles uniserial, 13—16. Wedgeshaped clump of
13—14 supraalar bristles extending slightly anterior to wing base. Anepisternal
suture length, 0.47 mm.
Wing. — Fig. 1. Terminal half of Ri thickened and fused to C. Short brist-
les along entire lengths of R, Ri, and R4+5. Alula hair fringe restricted to
middle half.
Leg. — Front L.R., 0.67. Hind L.R., 0.59. Apical bristles on fore and middle
tarsal segments 1—3, liind tarsi missing. Bristles absent from shafts of foretarsi,
present on middle tarsal segments 1—2. Empodium plumose, i/ó claw length.
Spermatheca. — Fig. 2. Two. Length, 0.12 mm. Width, 0.06 mm. Duets short,
running almost straight back to openings.
Genitalia. — Fig. 3. Cerci very large, yellowish.
REFERENCES
Edwards, F. W. 1922. On Diptera Nematocera from Spitsbergen. XXI. — Results
of the Oxford University Expedition to Spitsbergen, 1921 — No. 14. Diptera
Nematocera. Ann. Mag. nat. Hist. 10: 193—215.
Friðriksson, S. 1964. Um aðflutning lífvera til Surtseyjar. Náttúrufræðingurinn
34: 83-89.
Oliver, D. li. 1962. A review of the subfamily Orthocladiinae (Chironomidae,
Diptera) of Bear Island. Astarte 20: 1—19.
Pdlmadóttir, E. 1964. An island is born. Iceland Rev. 2: 18—21.