• Stephenson, Andrew G.

Catalpa speciosa is an obligate outcrosser pollinated diurnally by bumblebees and carpenter bees and nocturnally by various moths. More flowers are pollinated during the day, but there is no significant difference between day and night in the number of pollinations per hour. The quantity of nectar produced at night is significantly greater than during the day, but the sugar concentration of the nectar and the total sugar per flower is greater during the day. The quantity of nectar and sugar concentrations of C. speciosa flowers change from those typical of bumblebee-pollinated flowers during the day to those typical of moth-pollinated flowers at night.