42 Riley — Notefi on Yucca Insects and Yucca Pollination. 



cespitose species and placed in tlie subgenus Hesperoyucca. 

 The flowers are borne in immense panicles on a stalk which 

 arises directly from a crown of leaves near the ground and 

 reaches sometimes a height of twelve feet or more, and I present 

 herewith a photograph which very well illustrates the magnifi- 

 cence of some of the larger specimens (pi. ix). At my request 

 Mr. D. W. Coquillett, of Los Angeles, California, made some 

 special observations last year on the pollination of this species, 

 and on the 12th of June he was able to witness the operations 

 both of oviposition and pollination on a plant while yet the sun 

 Avas shining brightly, about fort}' minutes before setting. The 

 act of oviposition does not differ in any particular from that 

 which I have already described in detail for Pronuha yaccasella. 

 The pollen is deliberately gathered, and a mass nearly half the 

 size of the insect's head is held under her neck by the coiled ten- 

 tacles. In pollinating, the tentacles are uncoiled and stretched 

 so that the tips may be inserted into the upper part of the 

 stigma. "Sir. Coquillett describes the process of thus pollinating 

 the stigma as lasting about half a minute, after which the insect 

 that he watched descended tlie ovarv and at once mounted to 

 the top of one of the stamens. Here, with her tentacles, she re- 

 moved both pollen masses (moving her head from side to side 

 during the operation) and added the pollen thus gathered to 

 the mass which she was already carrying. She went to two 

 other stamens in succession, gathering a pollen mass from each. 

 Mr. Coquillett, in communicating his observations, remarks* that 

 " it was indeed surprising to witness the evident intelligence 

 which this insect displayed in all her actions wherever the ])istil 

 of the flower became pollinated solely through her own labors, 

 and that she went through these maneuvers with the evident 

 intention of pollinating the flower appears to admit of no doubt." 

 A number of insects have been observed associated with the 

 flowers of Yucca ivhi-pplei, but none of them as observed by Mr. 

 ('oquillett acted in an}'' way to produce pollination, either inten- 

 tionally or by accident. As a check to prove the influence of 

 Pronuba on the production of fruit, I desired Mr. Coquillett to 

 enclose another panicle and exclude the moths. We were both 

 somewhat surprised at the result, namely, that a certain num- 

 ber of the pods set on this panicle, and this would prove tliat 

 (so far as a single experiment justifies conclusion) the species is 

 capable of a certain amount of self-fertilization. 



