A SOUTHWESTERN PLANT GROUP. 801 



always the little moths of the genus Pronuba never any other in- 

 sect whatsoever. Several different species of Pronuba frequent re- 

 spectively several different species or groups of species of yuccas,* 

 but the most familiar one is the Pronuba yuccasella, always found 

 on our Yucca filamentosa, the most Northeastern type. Just about 



FIG. 10. FLOWER OF YCCCA GLORIOSA. 



nightfall, as the flowers open, the moths are seen flitting about 

 the yucca panicles. Usually the male is most constantly on the 

 wing, while the female is found running about within the flowers. 

 She begins operations by mounting the top of a stamen, exactly 

 as shown in Fig. 11. There she scrapes with her two odd hook- 

 like maxillary palpi the pollen out of the anther, and rolls 

 it into a globular mass under her head. With this load, often 

 thrice the size of her head, she goes to another flower, runs about, 

 apparently examines every nook and corner of it, and then, if per- 

 chance satisfied, finally settles astride two of the stamens with her 



* In the Report for 1893 of the Missouri Botanical Garden, Prof. William Trelease, Di- 

 rector of the Garden, publishes a paper on yuccas, from which the following notes are 

 made with reference to the Pronubas frequenting different species of the plant : Pronuba 

 yuccasella pollinates Y. jilamcntosci, Y. aloifolia, Y. glauca, Y. baccata, Y. gloriosa, Y. elata, 

 Y. glauca, var. stricta ; Pronuba synthetica pollinates Y. brcvifolia ; Pronuba macufata, Y. 

 Whipplei ; and Pronuba macnlata, var. aterrima (a new variety of Pronuba discovered by 

 Prof. Trelease in 1892), pollinates Y. Whipplei, var. graminifolta ; and, finally, Prof. Riley 

 predicts the discovery of distinct species of Pronuba on each of these yuccas, viz. : Y 

 tilif, >, Y. trcculeara, Y. Guatemalcnsis, and others. H. L. C. 



VOL. XLIII. 58 



