6 Mr. R. Patterson on the appearance of Clouds of Diptera. III. — Note on the appearance of Clouds of Diptera. By Robert Patterson, Esq., Member of the Nat. Hist. Soc. Belfast, &c. The appearance of Dipterous insects in large numbers is in certain localities and at certain times a matter of common ob-servation. About Lough Neagh myriads of Culicida, Tipulidce and Ephemerida are seen, and Culex detritus is recorded by Mr. Haliday* as rising above trees, so as to resemble the smoke of a cottage chimney. In Phil. Trans. 1767 5 it is stated that in 1736 the common gnat {Culex pipiens) rose in the air from Salisbury Cathedral in columns so resembling smoke, that many people thought the cathedral was on fire. In Norwich, in 1813, a similar alarm was created. At Oxford, in 1766, " a little before sunset, six columns of them were observed to as-cend from the boughs of an apple-tree, some in a perpendi-cular and others in an oblique direction, to the height of fifty or sixty feet ff A phenomenon similar to that last mentioned was this summer observed for some days at Belfast. Wherever there were trees, columns of insects were seen, and attracted the notice of even the most incurious. They began to appear a little before seven o'clock, and diminished in numbers as the light decreased, so that by half-past nine few were visible. On the evening of June the 1 1th, I went with Messrs. Bryce and Hyndman to the house of our fellow-member Mr. Grattan, situated on the north side of the bay, and about half a mile from the town, for the purpose of observing them. The fol-lowing notes were there drawn up, our remarks being limited to an irregular semicircular area, having an average diameter of seventy or eighty perches. The insects appeared in columns above the trees, the shade of colour varying according to the greater or less density of the mass from that of light vapour to black smoke, the co-lumns not only differing in this respect from each other, but each column being frequently different in different parts. They might have been mistaken for dark smoke-wreaths but for their general uniformity of breadth, and for a graceful and easy undulation, similar to that of the tail of a boy's kite, when at some height and tolerably steady. The individual insects flew about in each column in a confused and whirling multitude, without presenting in their mazy dance, any of those regular figures which gnats frequently exhibit over pools of water. The motion of their wings filled the air with a pe-* Entom. Mag., No. 11. p. 51. t Kirby and Spence, vol. i. p. 1 14.
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