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Mr. HULST'S OBSERVATIONS ON PRONUBA 

 YUCCASELLA. 

 By Prof. C. V. Riley. 



On page 1S4, current volume of "Entomologica Americana", Mr. 

 ( ieo. D. Hulst is reported as making the following statements in refer- 

 ence to Pronuba yuccasella, and I assume correctly since, being one of 

 the editors, he has opportunity to read and probably write his own state- 

 ments: 



"Prof. Riley, after many and extended observations, gave the his- 

 tory of the fertilization of this plant, concluding that the moth is a neces- 

 sity to the continuation of the plant, that fertilization was effected by it 

 alone and that every developed seed vessel bore evidence of the work of 

 the Moth bv the presence of the larvae within the capsule." 



He then refers to the method of oviposition and pollination by this 

 moth as described by me, and states that his observations have not 

 brought him to the same conclusion arrived at by me. He further states 

 his belief that there must be very extensive fertilization of this plant by 

 honey bees, because he found these '"plentiful about the flowers"; that 

 the majority of the seed capsules examined by him showed no indication 

 of larvae of any sort; and finally refers to the fact that Yucca is sometimes 

 fertile in foreign countries. 



There • much error and unwarranted conclusion in the two short 

 paragraphs in which the above information is vouchsafed. 



For over 16 years now I have very carefully studied the habits ol 

 Pronuba in connection with Yucca, not in one locality alone but in 

 nearly everv State east of the Rocky Mountains where that genus occurs 

 either indigenously or by introduction. I have also had occasion to 

 study it in many places in Europe in which it is cultivated, and the re- 

 sults have been published in several papers. 



In reference to honey bees frequenting Yuccas it is rather strange 

 .that Mr. Hulst's experience differs so from mine; for, so far as my ex- 

 perience goes, neither honey bee nor any other honey-loving Hymenop- 

 te.ra frequent the Yucca flowers and this is what we should expect from 

 the very nature of these flowers They are half closed during the dai 

 and do not open until toward evening when bees are hiveward bound: 

 the anthers do not open till then and the pollen is glutinous,adheringin 

 lumps either on the curled anthers or to the inside of the perianth. It 

 would not adhere to hirsute Hymenoptera, and in point of fact these are 

 not found in the flowers. I have given a list of the insects most freqo nt 



