Patterns of daily mating activity in 4 spp. of Micrathyria were determined by hourly censuses at sites in the Panama Canal Zone, M. atra and M. ocellata appear at breeding sites before sunrise and are present until late afternoon, but the time of maximum activity varies depending on the abundance of congeneric spp. and secondarily on physical factors in the environment. The smaller spp,. M. aequalis and Micrathyria sp. A (nr. eximia) are invariably active only from mid-morning until mid-afternoon. The presence of 99 at breeding sites does not always coincide with maximal <5 activity. Less complete data are available for several other spp. in the Canal Zone and Costa Rica. — M. atra dcJ remain at breeding sites only 3-4 hrs at a time, while M. ocellala and M. aequalis individuals often are present for 8-9 hrs. Individuals of all spp. vary from day today in timing of activity and position of local territory. Aggressive interactions are common between Micrathyria spp. and with several unrelated spp. The number of aggressive encounters of individual ocellata with aequalis depends strongly on the density of aequalis present. These 2 spp. overlap considerably in perch choice. Distribution of food within the alimentary tract of atra and ocellala suggested that they do not feed at breeding sites and that most individuals present before mid-morning have not fed since the previous day.