FURTHER STUDIES OF YUCCAS. 203 



species of small bees* were taken, probing the outlets of 

 the conducting grooves at the base of the pistil ; but these 

 insects were not seen to visit the stigma, so that they 

 play no part in pollination. Considerable numbers of a 

 moth, which Professor Riley determines for me as Acontia 

 Arizona, Hy. Edw., were seen resting in the flowers during 

 the day, and settled about them, especially on the pedicels 

 near the base of the perianth, at night, but I was not 

 fortunate enough to determine the occasion of their visits 

 to the plant, though I suspected that their larvae might 

 develop on it. So far as can be seen, they play absolutely 

 no part in its pollination, though it may be that they feed to 

 a greater or less extent on the nectar. The stamens shed 

 their pollen promptly on the opening of the flowers, and 

 this is devoured by various small flies with the same avidity 

 as in glauca, and with about the same prospect of effecting 

 occasional casual pollination as in that species. f 



Like the eastern Yuccas, elata is pollinated by Pronvba 

 yuccasella, the work of which was repeatedly observed in 

 detail at Eagle Flat, where the moths were abundant. 

 During the day, like the Eastern moths and those of baccata, 

 they rest in the flowers with their heads directed to the base 

 of the petals. Shortly before sunset many of them be- 

 come active (as is the case on filamentosa at St. Louis), 

 the females beginning their work of oviposition and pol- 

 lination, while the males run and fly actively from flower 

 to flower in search of their mates ; and this is continued 

 through the greater part of the night. 



When about to deposit an egg, the moth here, as on 

 filamentosa, runs nervously about within the bottom of the 

 flower, then scrambles to the top of the pistil and backs 

 down between two stamens by a succession of jerks until 

 her head is about level with the base of the style. Hold- 

 ing to the pistil by the pro- and meso-thoracic legs, the last 



* Determined by Mr. Charles Robertson as Agapoatemon Texanus, tf, 

 and Hulictus albipennis, 9 • 

 t See a note by the writer in Riley, I. c. 125. 



