Glyphipterix; FOOD-PLANTS; Hyptis urticoides; Gall induction, prevalence, life cycle & hymenopteran parasites; LIFE-CYCLE; Synchronization with food plant gall development; HYMENOPTERAN-PARASITES; Ephialtinae; Parasite records from food plant galls; COSTA-RICA; Heredia province, Barva; Food plant gall formation, life cycle & hymenopteran parasite records Ephialtinae; LEPIDOPTERAN-HOSTS; Glyphipterix; Host records from plant galls; COSTA-RICA; Heredia province, Barva; Lepidopteran host records The stem galls made by Glyphipterix sp. were studied in a natural population of Hyptis urticoides in Heredia, Costa Rica, during 1986-87. About 25% of plants had galls and 150 galls were examined. There were 2 periods of gall formation in May-June and August-September. The internal structure and growth of galls are described. The withering of the stem apex marked the beginning of a gall in the stem. Gall growth was caused by penetration of a I st-instar larva into the stem. About 60 days elapsed between gall initiation and degeneration. Development from the I st instar to the adult was synchronized with gall development. Ichneumonid parasitoids of Glyphipterix sp. were found in galls. none - no species