LITERARY NOTICES. 



Interrelations between Plants and Insects. i 



Few recent additions to the subject of instinct are more significant 

 than the contrilnition above referred to. The remarkable habit of the 

 yucca motli of carefully cross-fertilizing a plant, in order that the egg 

 which it deposits in the ovary of the plant may find suitable conditions, 

 seems at first as difficult to explain by an appeal to instinct developed 

 under natural selection, as it is incredible when considered the result of 

 analytic intelligence. The flowers of the yucca are produced in large 

 panicles and are characterized by the anthers not reaching anywhere near 

 the stigma, so that self-fertilization could take place only by the merest 

 accident. The stigmatic opening is at the tip of the prolonged style and 

 is nowhere within reach of the stamens, while the pollen either remains 

 attached to the withered anthers or falls in lumps to the bottom of the 

 perianth. It cannot be introduced into the stigmatic tube without arti- 

 ficial aid and the plant depends absolutely on the little white moth 

 known as Pronulia. 



While the male of this moth resembles others of the family 

 [Tincina] the female has remarkable structural peculiarities, which ad- 

 mirably adapt her for the functions she has to perform, for she must fer- 

 tilize the plant, since her larva^ feed upon its seeds. A pair of maxillary 

 tentacles which are prehensile and spinous on their under surface are pe- 

 culiar to the genus Pnnmba and exist in no other genus of the over 24000 

 described Lepidoptera. A long and peculiarly modified ovipositor, re- 

 sembling that of certain Hymenoptera, is another peculiarity. It is by 

 means of the latter with its saw-like appendage that the eggs are inserted 

 within the ovary of the yucca. 



As preliminary to this process the female collects a load of pollen, 

 during which process the maxillary palpi are used in scraping the pollen 



1. Riley, C. V. Some luterrelations of Plants and Insects. Proc. Biol. Soc. of 

 Washington. Vol. VII, May 2!i, 1892. 



