FIELD BOOK OF INSECTS. 



pupate. The adults have a wing expanse of about three- 

 quarters of an inch; the bases of the front wings are black, 

 the rest being white, clouded with gray; the hind wings 

 are light gray ; the head bears long white hairs. The larvae 

 of all three species feed on hair, wool, feathers, and almost 

 any fabric of animal origin except (?) silk. 



Larvas of Prodoxus intermedius bore in stalks of Yucca 

 in great numbers. 



"No discovery in recent years has been 



onuba more interesting to students of insect and 



yuccasella 



plant life than that which was made in 



1872 by Professor Riley, of the intimate relationship which 

 subsists between the beautiful plants, known as Yuccas, 

 and the genus of moths to which the present species 

 belongs. It has been ascertained that the fructification 

 of the various species of Yucca is almost absolutely de- 

 pendent upon the agency of the female moth ; and, strangely 

 enough, it has also been ascertained that the pollination 

 of the flowers is not the result of mere accidental attribu- 

 tion of the wings and other organs of the insect when 

 engaged in seeking for nectar in the flower and when 

 engaged in laying her eggs, but that she deliberately 

 collects the pollen with her mouth, which is peculiarly 

 modified to enable her to do this, and then applies the 

 pollen to the stigma with infinitely better care than it 

 could be done by the most skillful horticulturist using 

 the most delicate human appliances" (Holland) The 

 moth's actions are not altogether altruistic for she lays her 

 eggs in the seed capsules and her young feed on the tissue, 

 which would not develop if she did not pollinate. When 

 full-grown, the larva crawls out and hibernates in a tough 

 cocoon on or in the ground, pupating when spring comes. 



The HEPIALID^E, Ghost-moths, and MICROPTERYGID^E, 

 belonging to the suborder MICROPTERYGOIDEA, con- 

 tain small, rare moths closely related to the Trichoptera, 

 Caddie e-flies; see p. 57. The larvag of some, at least, of 

 the Hepialidae bore in roots; those of Micropterygidae are 

 usually leaf-miners. 



228 



