Lygaeus equestris breeds in open areas. It overwinters in the adult stage, and in the autumn and spring it undertakes migratory flights to and from its hibernation sites. It feeds on the generative parts of a variety of plants. During I969 the population trends of L. equestris and of the flower and seed production of its food plants were studied in eight habitats. High numbers of L. equestris always coincided with peaks in flowering or seed production of the food plants. The spring migration was simultaneous with the start of flowering of the earliest food plants. The autumn migration, however, started when food resources still seemed ample. During the summer, nonmigratory (trivial) flights were important for the bug to keep pace with the changes in food availability. In I970 the distribution of food resources was quite different to that in I969, and consequently the invasion of habitats followed a different pattern. Four periods of flight were recognized: (I) postteneral trivial flights, (2) autumn migration, (3) spring migration, and (4) trivial flights of overwintered bugs. Possible causes of the different types of flight are outlined. The dispersal capacities of the bug are regarded as adaptations to the temporariness of its habitats. The implications of the flight movements on the population dynamics of L. equestris are briefly discussed.