ANIMAL BEHAVIOUR 199 



of ganglia which are able to control many actions by them- 

 selves. We must remember that a wasp or a bee may go 

 on feeding after its tail has been cut off, as Baron Mun- 

 chausen's horse went on drinking after most of its body had 

 been shot away. Even a decapitated insect can do a good 

 deal, like St. Denis who walked round the town with his 

 head in his hands. But whatever may have been the saint's 

 reflections, we may be sure the insect has none. 



Before going further let us take a thoroughly typical 

 instance of instinctive behaviour, and there is no better 

 than that of the Yucca Moth (Pronuba yuccasella), which 

 has been often cited. When the large yellow bells of the 

 Yucca open, each for a single night, the silvery moth, just 

 emerged from her chrysalis, sets forth to visit them. From 

 the anthers of one she collects pollen, which she kneads into 

 a ball, and holds beneath her head. She flies to another 

 flower, pierces the pistil with her ovipositor, lays her eggs 

 among the ovules, and then places the fertilising pollen- 

 pellet in the funnel-shaped opening of the stigma. Without 

 the pollen thus brought by the moth the ovules would not 

 develop. The larvae of the moth eat a share of the developing 

 ovules, but not more than about half are required. So that 

 both plant and insect are served. In referring to this ex- 

 traordinary case Prof. Lloyd Morgan writes: "These mar- 

 vellously adaptive instinctive activities of the Yucca moth 

 are performed but once in her life, and that without in- 

 struction, with no opportunities of learning by imitation, 

 and, apparently, without prevision of what will be the out- 

 come of her behaviour; for she has no experience of the 

 subsequent fate of the eggs she lays, and cannot be credited 

 with any knowledge of the effect of the pollen upon the 

 ovules. The- activities also illustrate what is by no means 



