and presently will eat tii . out of the ovary 



and fall to the ground, wiierc they will bury 

 tbemaelvet for a aeaaoD; ooming forth as adult 

 moths in the succeeding summer, just at the time 

 wha the yucca is flowering. 



SUTICB FOE SEETICS 



At first glance it is not obvious h^^^ ♦^'» yucca 

 profits by this curious arrangement . 



But observation Aown that the progeny of the 

 moth seldom or never consume all the yucca seeds 

 that are so conveniently stored about them. After 

 they have eaten their fill and have sought a new 

 shelter, enough yucca seeds remain to insure per- 

 petuation of the species. The progeny of the 

 moth have indeed taken toll of part of the crop 

 of yucca seeds in recompense for the services 

 performed by their mother. 



But, on the other hand, had the moth not paid 

 its visit, the flower would by no chance have been 

 fertilized at all. 



Here, then, is a case in which there is absolute 

 mutual dependence between a partictilar species 

 of insect and a particular species of plant. In 

 the desert regions it inhabits the moth could find 

 no other place to deposit her eggs where food 

 would be assured her off«:r»ri*ng; and in the bum- 





