_Cecidomyia frauenfeldi_ was named by Dr. Schiner after the naturalist who collected the galls on _Leptospermum_ in the vicinity of Manly, N.S. Wales. These galls are produced upon a leaf-bud and consist of a number of rounded leaf-like bracts, not unlike the petals of a rose bud; folding over each other, brown in colour, soft and loose, and about the shape and size of a small marble. The enfolded larva will be found in the base at the centre, and the gnats can be easily bred out in a glass jar. The Acacia Gall-gnat, _C. acaciae-longifoliae_, infests the flowers of this wattle, depositing its eggs in such numbers that every tiny seed-pod is produced into a contorted mass of finger-like tubes, together forming a rounded base attached by a stalk, and each tube containing a larva. This is one of our commonest species and the galls can often be collected in numbers in the neighbourhood of Sydney. _Diplosis frenelae_ produces very remarkable little light brown spherical structures upon the tips of the foliage of the desert cypress, about the size of small peas; these when mature split into four shell-like sections, quite unlike the usual gall. They are very abundant in the early summer upon cypresses in Wagga and the western pine scrubs of N.S. Wales. _Diplosis paralis_ forms curious little blisters upon the young foliage of _Eucalyptus corymbosa_, dotting the leaves all over with reddish spots with a keyhole-like mark on the apex. A third species, _D. eucalypti_, aborts the young twigs of Eucalypts into gouty swellings in which a number of larvae feed and pupate. There are certain red rounded shot-like galls of the Eucalyptus, generally several in number on the midrib of the leaf, which, on account of the pupal skins always remaining in the holes in the sides of the galls through which the flies have escaped, can be easily distinguished from many very similar ones that are the work of micro-hymenoptera. These are formed by a large stout gnat named _Hormomyia omalanthi_ by Skuse, who first obtained specimens from galls on the under side of the leaves of _Omalanthus populifolius_. _Lasioptera miscella_ aborts the leaf stalks of _Eucalyptus haemastoma_, one of our white stemmed gums growing about Botany, N.S.W., with its irregular swellings. I have also bred several undetermined species from galls on the twigs of the Weeping Myall, _Acacia pendula_, and other wattles in the western scrubs. There is a rich field awaiting the naturalist who takes up the study of the life-history of our Gall-gnats.