Black Variety of Pronuba maculata. 45 



A further interesting fact connected with the pollination of 

 this species is that Professor Trelease discovered a purely black 

 variety (which he describes as aterrima) of Pronuba maculata con- 

 nected with the variety graminifolia (Wood) of Yucca whipplei, 

 common in San Bernardino county. The actions of this black 

 variety are similar to trrose of the typical form, and it is also 

 diurnal rather than nocturnal in its movements. The method 

 of gathering the pollen mass is thus described : 



" Flying into a flower, the moth runs about the bases of the stamens 

 after the manner of other species, then quickly clambers upon the inner 

 side of a filament, and, with the tentacles extended over the pollinia, 

 drags first one and then the other out of the anther cells, pressing them 

 together under the throat, and subsequently compacting the mass to- 

 gether, much as yuccasella does the powdery pollen of other Yuccas, so 

 that the ball finally consists of as many as ten or a dozen pollinia. So 

 quick and energetic are the motions by which the pollinia are removed 

 that the stamens are often shaken quite violently, as I have before noted 

 in the more nervous attempts of yuccasella" 



PRONUBA YUCCASKLLA ON THE PACIFIC COAST. 



Of the fleshy fruited Yuccas Professor Trelease was able to 

 study, among others, Yucca baccata Torrey, which is pollinized 

 by Pronuba yuccasella. While he was not able to observe the acts 

 of pollination, all the circumstances and the facts which he ob- 

 tained would indicate that it is precisely the same as described 

 for other species of Y r ucca that are fertilized by this moth, and 

 the fertilized flowers show " conclusively that the pollen is thrust 

 well into the stigmatal canal,'' or in some cases apparently even 

 into "the top of the ovarian cells, which, owing to the short 

 style and the deep stigmatic notches, they [the moths] can reach 

 easily with their long maxillary tentacles." The moths taken 

 from flowers at Cabazon and San Diego are somewhat above 

 the average in size, with the horny and chitinous parts somewhat 

 darker than in the typical form, but specimens which he sent 

 me cannot be considered to have even varietal differences, and 

 find their counterparts in my cabinet in specimens from Dakota 

 and Colorado. 



Yucca rapicola Scheele, of southern Texas, and Y. elata Engelm., 

 extending from southern Texas to southern Arizona, are both 

 pollinated by Pronuba yuccasella, as Professor Trelease ascer- 

 tained, 



