Page:Popular Science Monthly Volume 43.djvu/821

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A SOUTHWESTERN PLANT GROUP.

always the little moths of the genus Pronuba—never any other insect whatsoever. Several different species of Pronuba frequent respectively several different species or groups of species of yuccas,[1] but the most familiar one is the Pronuba yuccasella, always found on our Yucca filamentosa, the most Northeastern type. Just about

PSM V43 D821 Flower of yucca gloriosa.jpg
Fig. 10.—Flower of Yucca 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 hooklike 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 perchance satisfied, finally settles astride two of the stamens with her


  1. In the Report for 1893 of the Missouri Botanical Garden, Prof. William Trelease, Director 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 yucasella pollinates Y. filamentosa, Y. aloifolia, Y. glauca, Y. baccata, Y. gloriosa, Y. elata, Y. glauca, var. siricta; Pronuba synthetica pollinates Y. brevifolia; Pronuba maculata, Y. Whipplei; and Pronuba maculata, var. aterrima (a new variety of Pronuba discovered' by Prof. Trelease in 1892), pollinates Y. Whipplei, var. graminifolia; and, finally. Prof. Riley predicts the discovery of distinct species of Pronuba on each of these yuccas, viz.: Y. tillfera, F. treculeara, Y. Guatemalensis, and others.—H. L. C.