The Sea-Midge and its Larva

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THE SEA-MIDGE AND ITS LARVA.

THE SEA-MIDGE AND ITS LARVA. BY CLAUDE MORLEY, F.E.S., F.Z.S., DESPITE the fact that the Insecta " is, beyond

&c. all comparison, the most populous Class of animals, embracing as it does more than ten times as many species as all other living beings put together, the sea is singularly destitute of them. It has been frequently said that no true Insect is marine ; and, though this is not literally true, the minuteness of the exception makes the rule even more striking than it would have been if absolutely universal. Of the hundreds of thousands of Insects known to exist, but two live in the sea, and both of these may be found on our own coasts. However there is, besides these, the larva of some two-winged Dipterous fly, which is marine. I have repeatedly taken it on our southern shores, quite out of the influence of fresh water," wrote Philip Henry Gosse some eighty years ago (Manual Marine Zoology 1855, i, 178), lucidly exhibiting the extent of knowledge upon the subject at that period. His Fly was not the present Midge ; for he adds (lib. cit. ii, 217) its description. Our Midge rejoices in the name Thalassomyia Frauenfeldi Schiner ; and the earliest specimens of it noted in Suffolk were two males, taken by me on the sea-beach at Dunwich upon 9 September 1921. These were presented to the National Collection, whence Mr. Edwards recorded themfirstfrom " Suffolk " merely, Cornwall, Devon and Somerset alone in Britain, during 1929 (Trans. Ent. Soc. lxxvii, p. 371). Fora decade no more were observed here ; tili a great number occurred to me, running just at high-tide mark erratically and excitedly over the green sea-weed [Viva laduca, Linn.) that was interspersed with, small Barnacles (Baianus balanoide Linn.), growing on the vertical timbers of a large breakwater, on Gorleston beach at dusk of both 6 and 7 May 1931. When boxed, the female sits quiescently; but the male runs about actively, with its wings half-spread, making jumps rather than flights of no more than an inch in length. Our Member, Mr. Ellis, had already noticed a Midge in the same Situation, as well as a reddish larva under Viva that he expected would prove to be its immature form ; the latter seemed to be present just below high-water mark all the year round, as was especialy observed in November. Early in the following September he was so good as to give me several of these larvse, along with mature T. Frauenfeldi, thence for description. THE LARVA (somewhat immature) is subcylindrical and but slightly attenuate towards the anal extremity, apodous and with out apparent setas, olive-green when in Chlorospermeous algae, but pink when in Rhodospermeous, and subtranslucent with thirteen segments. Two first segments


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