ABSTRACT. 1. Megaloceraea recticornis (Geoffroy) is the most common of seven species of stenodemine bugs on a calcareous grassland in Oxfordshire. Previous work indicated that it competed with a related species, Notostira elongata Geoffroy, by behavioural interference at the feeding site. Both bugs were thought to eat only grass leaves.
2. The importance of grass flowers in the diet of M.recticornis was studied in the laboratory. This bug completes its development only by feeding on grass flowers; grass leaves do not suffice.
3. M.recticornis is unusual among phytophagous insects in that its later instars can eat flowers of the grass Brachypodium pinnatum L. The hard lemma and palea surrounding these flowers inhibit feeding by young bugs. The age of the flowers also affect bug feeding success.
4. The result of field experiments, which previously appeared to show competition between M.recticornis and N.elongata, are discussed in the light of the present findings. It now seems that M.recticornis may not suffer from competition with N.elongata.