NOVEMBER 287 



the insect acting with as much circumspection and 

 precision as could be shown by a human cultivator. 

 Such is the behaviour of the yucca moth (Pronuba 

 yuccasella). This insect haunts exclusively the flowers 

 of the yucca, and, collecting pollen from one blossom, 

 kneads it into a pellet which she is said to carry by 

 means of specially enlarged palps to another flower. 

 Here she pierces the pistil and deposits her eggs among 

 the ovules or unfertilised seeds, and then swiftly runs 

 to the top of the pistil and pushes the pollen-pellet 

 into the wide mouth of the stigma. Observe, that 

 without this interchange of offices between insect and 

 plant, the race of each would cease to exist. I am told 

 that it has been proved that the ovules cannot be 

 fertilised unless pollen, preferably from another blossom, 

 is intentionally inserted into the funnel of the stigma ; 

 if they were not so fertilised they would afford no food 

 for the grubs of the ministering moth. When all goes 

 well, the grubs eat about half the ovules, leaving a 

 hundred or so to ripen as seeds, and to perpetuate the 

 herb which is essential to the existence of the moth. 

 It is difficult to recognise merely sentient automatism 

 in the means by which this interdependence of host and 

 guest is maintained, the action closely resembling that 

 of effective consciousness. Yet if it be extravagant to 

 attribute to the moth an understanding of vegetable 

 physiology, what is left but to speculate upon the 

 source whence the race of Pronuba derives the impulse 

 directing each individual female moth to go through 

 the very same complex performance ? ' Amid the 

 mysteries,' wrote Herbert Spencer, 'that become the 



