224 



ENTOMOLOGY 



of the pistil appears to be of no consequence, at present, and the stig- 

 matic fluid is not nectarian; indeed, the tongue of Pronuba, used in 

 clinging to the stamen, seems to have lost partially or entirely its 

 sucking power, and the alimentary canal is regarded as functionless. 

 Ordinarily it is the flower which has become adapted to the insect, 

 which is enticed by means of pollen or nectar, but here is a flower which 

 though entomophilous in general structure has apparently adapted 

 itself in no way to the single insect upon which it is dependent for the 

 continuance of its existence. More than this, the insect not only labors 



FIG. 261. Pronuba yuccasella, 

 female, gathering pollen from anthers 

 of Yucca. Enlarged. 



FIG. 262. Pronuba moth ovipositing in flower of 

 Yucca. Slightly reduced. 



without compensation in the way of food, but has even become highly 

 modified with reference to the needs of the plant, its special modifica- 

 tions being unparalleled among insects with the exception of bees, and 

 being more puzzling than the more extensive adaptations of the bees 

 when we take into consideration the impersonal nature of the operations 

 of Pronuba. Further investigation may render these extraordinary 

 interrelations more intelligible than they are at present. 



The bogus Yucca moth (Prodoxus quinquepunctella) closely resembles 

 and associates with Pronuba but oviposits in the flower stalks of Yucca 

 and has none of the special adaptive structures found in Pronuba. 



As regards floral adaptations, these examples are sufficient for pres- 

 ent purposes; many others have been described by the botanist; in fact, 

 the adaptations for cross pollination by insects are as varied as the 

 flowers themselves. 



