Characteristics of Promt /><r. 83 



of the Mohave Desert and filifara. of Mexico. My re- 

 marks will be based chiefly on Yucca filamentosa, which is indig- 

 enous to the Southeastern States and is cultivated beyond its 

 natural range, under a number of horticultural variety names, 

 in our gardens. 



An examination of the flower will show at once the peculiar- 

 ities which I have alluded to as characteristic of the genus. The 

 stamens or filaments are bent away from the stigma and do not 

 reach more than two-thirds the length of the pistil, the stigmatic 

 opening being at the tip of the prolonged style and nowhere 

 within reach of the stamens, while the pollen either remains 

 attached to the open and withered anthers or falls in different 

 sized* lumps on the underside of the perianth. It cannot be 

 introduced into the stigmatic tube without artificial aid, and the 

 plant depends absolutely on the little white moth belonging to 

 the Tineina and known as Pronuba yuccasella Riley. 



STRUCTURAL CHARACTERISTICS OF PRONUBA. 



Upon a superficial view, this little moth shows nothing very 

 peculiar. The general coloration is white, the primaries being 

 purely white on the upper surface ; so that when at rest in the 

 half open flowers of the Yucca it is not easily detected. The 

 under surfaces, however, are dusky and offset in flight the white- 

 eness of the rest of the body, so as to render the species some- 

 what difficult of detection while flitting from plant to plant. 

 The male shows no very marked peculiarities to distinguish him 

 from the other members of the family, the most noticeable being, 

 perhaps, the prominence of the exposed parts of the genitalia. 

 The female, however, shows some remarkable structural pecu- 

 liarities, which admirably adapt her for the functions she has to 

 perform, for she must fertilize the plant, since her. larva? feed 

 upon its seeds. 



Now. if I should ask any well-informed entomologist what 

 are the characteristics of the Lepidopterous mouth, in the imago 

 state, he would unhesitatingly answer : The lack of all prehen- 

 sile organs and a coiled tongue capable of sucking liquids. If 

 again I should ask what distinguishes the Lepidoptera from, 

 say, the Hymenoptera, in the methods of oviposition, he would 

 answer that the Lepidoptera lay eggs possessing, it is true, an 

 infinite diversity of form, but usually attached externally to 

 some part of the food-plant of the species, while the Hymenop- 



