Pollination of other Species of Yucca. 95 



thick and leathery petals, but very abnormal in the Lepidoptera. 



In fact, this species strongly recalls in its general aspect some of 

 the saw-flies belonging to the genus Dolorus, the resemblance 

 being heightened by the rather conspicuous, cenchri-like spots, 

 and by the conspicuous division between thorax and abdomen. 

 It also strikingly recalls some of the Neuroptera, as Sialis infutnata. 



Now these resemblances to insects of different Orders and to 

 families which are generally conceded to be of low type within 

 their Order, cannot possibly be mimetic, as there can be no con- 

 ceivable cause, purpose, or advantage in the mimicry. It is also 

 impossible to account for these resemblances upon any present 

 genetic connection. Yet we are hardly justified in disposing of 

 them as merely accidental and without meaning. They suggest 

 a possible synthesism in the past, when types were less special- 

 ized and present Orders had not become so well differentiated. 



Yucca whipplei) which occurs in southern California, has flowers 

 distinguished by their relatively long and stout stamens, the 

 pollen of which is copious and glutinous, not to say mucilag- 

 inous, and a short, contracted style, with the stigma, however, 

 expanded and covered with sticky threads. It is pollinized by 

 Pronuba metadata Riley, which, as already shown, has a tongue 

 modified into an accessory pollen-gathering organ. If any 

 species of Yucca would seem not to need a special insect for pol- 

 lination, Yucca whipplei is that species ; for the long stamens, the 

 sticky and abundant pollen, and the peltate, hairy stigma would 

 all seem to facilitate ordinary pollination. Nevertheless, the 

 very restricted style would seem to be purposely developed to 

 counteract these other facilities, and we find a Pronuba asso- 

 ciated with it, with a remarkably modified tongue, and with the 

 maxillary tentacles very long and attenuated at the tip struct- 

 ures which doubtless enable the moth to perform the act of pol- 

 lination. I have never been able to observe the act, nor has any 

 one yet recorded either the acts of pollination or oviposition. 

 There will be nothing peculiar about the latter, but I shall be 

 very glad to get actual experience in reference to the former, as 

 I am satisfied that the observed facts will show, still more fully 

 than in the case of Pronuba yuccasella, that the special modifica- 

 tions of both flower and insect have gone on until the mutual 

 interdependence has become absolute. 



There is much yet to learn of the pollination of other species 

 of Yucca, and I am particularly anxious to obtain the insects 

 which will doubtless be found associated with them. The regal 



