Attraction of maleMicroplitis croceipes(Cresson) to virgin females was demonstrated for the first time in the field. The males were most active during morning hours beginning as early as 0630, with peak numbers occurring between 0800 and 1100. No males were caught in traps baited with virgin females after 1200. Female flight activity also was greater in the morning than in the evening, but females remained active throughout the day. Flight activity of females began about 1 h later than males. No significant (P<0.05) difference in parasitism byM. croceipeswas detected for host larvae (Heliothisspp.) that were collected from different areas of the cotton plant, or that were feeding on squares, versus flowers versus bolls. Parasitized larvae were collected from all sizes of cotton bolls (up to 40 mm in diameter), but no large (25− to 40−mm) larvae that were collected from the field were parasitized byM. croceipes.