Foraging activity ofMegachile lanata onCrotalaria juncea L. flowers occurred only when minimum threshold of environmental factors was surpassed, while the cessation of activities was governed mainly by the fast decline in values of light intensity and solar radiation. Between the initiation and cessation of field activity, foraging population showed a positive correlation with air temperature, light intensity, solar radiation and nectar-sugar concentration fluctuations, but was negatively correlated with relative humidity, soil temperature and wind velocity. The path coefficient analysis revealed that direct effect of solar radiation and light intensity on foraging population were much pronounced and positive, while the effects of other factors were of very low magnitude, negative or negligible. However, their interrelationships caused accentuation of the overall effects of air temperature, relative humidity and nectar-sugar concentration. The resultant correlation with bee activity were strengthened through their favourable or unfavourable interaction with other factors.