Summary.1The species of gall midges whose larvae live in the stems of willows have been briefly reviewed.2It is pointed out that, in the past, the so‐called “shot hole” midge damage on willow stems and branches has been frequently ascribed toR. saliciperdaDufour without considering either the insect itself or the species of willow.3This study has shown that several species of gall midges are responsible for this type of damage and that, so far as can be ascertained from an examination of cultivated species of willows, withS. fragilisin addition, each species of midge is restricted to one (in one case three) species of willow.4The adults, pupae and larvae ofR. saliciperdaDufour,R. triandraperdasp.n.,R. purpureaperdasp.n. andR. justinisp.n. have been described.5The bionomics of these species have been worked out. It has been found that, while all multiply by means of unisexual families, the first three species are single brooded but thatR. justinisp.n. has two broods a year.R. saliciperdaDufour lives onS. caerulea, S. fragilisandS. alba(Cecconi),R. triandraperdasp.n. will only attackS. triandra, whileR. purpureaperdasp.n. andR. justinisp.n. are restricted toS. purpurea.6The nature of the damage caused by the larvae of these midges has been described and control measures have been discussed. Tarring the stubs has been mentioned. It is suggested that cutting down the new growth in May, where practicable, would reduce the midge infestation. This latter treatment has the additional advantage of getting rid of initial caterpillar and frost damage which result in dead terminals and so produce side‐branching close to the stubs. Wild Crack willow (S. fragilis) should be destroyed as it can act as a reservoir forR. saliciperdaDufour.7Keys have been drawn up for the identification of the midges using host plants, larval, pupal and adult female characters.8The following parasites are recorded—Torymidae:Torymussp., nearauratusFonsc; Eurytomidae:Eurytoma aciculataRatz.,E. saliciperdae. Mayr.: Pteromalidae:Tridymus salicisNees; Eulophidae:Pleurotropis? caenusWalk.,Tetrastichus flavovariusNees,T. roesellaeDe Geer; Platygasteridae:Platygaster cecidomyiaeRatz.,P.sp. (?phili