The flies emerge from the pupæ in August and September, after which the females quickly seek the winter corn, and lay their eggs singly or in pairs on the leaves of the yet young plants. The larvæ creep between the leaf-sheath and the still quite undeveloped haulm, and, in the case of small haulms, a number of larvæ may collect together in the immediate neighbourhood of the root, causing a spherical swelling. In many cases the plant dies if its lower parts are inhabited by many larvæ. Before winter, the larvæ attain their full size, leave the plants, and creep into the soil, where, in the following spring, they become pupæ, from which flies emerge fourteen days later. There are, therefore, two generations annually. The _spreading_ of Hessian flies into regions where they were formerly unknown may be caused by (_a_) straw containing the linseed-like pupæ (straw for paper manufacture, packing, etc.); (_b_) grain, among which are often found pupæ that have fallen out of the haulms among the separated grain. _Remedies_: 1. Sowing the winter grain as late as possible, so that the females of the summer generation when they come out of the pupæ will find no winter-grain-plants in which to lay their eggs. 2. Ploughing up the stubble immediately after harvest, or else burning it, so that the pupæ found above the lower nodes are either deeply buried or else burnt. The =Scarlet Wheat Midge= (_Cecidomyia equestris_). Female about ⅛ inch, male ¹⁄₁₂ inch; cherry red, with yellow hairs; back of the thorax dark brown. Antennæ as long as the body in the male, half as long in the female. On the wing from May till June; lays its eggs on the leaves of grain-plants, at the base of the uppermost leaf by preference. The blood-red maggots, when they are hatched, let themselves slide down, and get between the leaf-sheath and haulm. Here they work themselves into the haulm, making a longitudinal groove, the walls of which swell more or less, and the end of which is indicated by an obvious transverse thickening. The leaf-sheath hiding the attacked part of the stem is usually more or less swollen. These gall-like outgrowths take up a great deal of nutritious matter, not only from the affected haulm but also from the plant at large, so that the regions not directly attacked are retarded in their growth. The larvæ are full-grown at harvest time, leave their hiding-places, and let themselves fall to the ground, where the following spring they become pupæ, from which midges quickly emerge. _Remedy_: After a year in which the insect has caused great damage, the fields must be deeply ploughed in order to kill the larvæ, which would otherwise live through the winter. The =Wheat Midge= (_Cecidomyia tritici_). [Illustration: