This is another very abundant species, found occasionally amongst rotten wood in very large communities. Its larva, which is represented at Fig. 5b, does not form any cocoon, the pupa being quite naked and defenceless. It is a beautiful little object when examined with a microscope of moderate power. The annual migration of the winged males and females of this species usually takes place on a hot day in the last week of March, at which time I have observed the air throughout a day's journey absolutely swarming with these little insects. Many specimens are captured in the spiders' webs, while the logs, fences, and ground are covered with ants in the proportion of about ten males to one female. At other seasons of the year the winged individuals of _Atta antarctica_ are seldom observed. Family CHALCIDIDÆ. _Pteromalus_ sp. (?) (Plate III., fig. 9). This little insect was reared, in company with thirteen others of the same species, from a pupa of _Eurigaster marginatus_ which had been procured from a larva of _Oeceticus omnivorus_, and is consequently a true hyperparasite.[3] Its curious habits will be better understood by the reader after perusal of the life-histories of those two insects, which I have given on pages 60 and 74. The method by which the females of the Hymenoptera whose larvæ are parasitic on insects inhabiting other insects, {38}introduce their eggs into their hosts,[4] is not at present known to entomologists, but it seems at least probable that they are deposited in the eggs of the parasitic Dipteron before these gain access to the caterpillar of the moth. Family ICHNEUMONIDÆ. _Ichneumon sollicitorius_ (Plate III., fig. 6). This is the most abundant of our ichneumon-flies, and may be taken amongst herbage from August till May. Its larva is parasitic in the caterpillars of various Noctuæ, having occurred in the following species: _Mamestra composita_, _M. mutans_, and _M. ustistriga_. The pupa may be frequently discovered inside that of the moth, and is quite white in its early stages, but as age advances all the colours of the future insect can be seen through the thin pellicle which invests it. The perfect insect makes its escape through a circular hole, which it drills in the upper end of the unfortunate moth pupa it has destroyed. The sexes of all ichneumon-flies may be at once recognized by the females possessing an ovipositor[5] differing considerably in length among the various species, but nearly always plainly visible. Family ICHNEUMONIDÆ. _Ichneumon deceptus_ (Plate III., fig. 7).