PLANTS AND INSECTS 



117 



Now, why does this female Pronuba moth do all this ( 

 It has been shown that down in the stigmatic opening 

 there is no nectar to attract her; she does not eat 

 pollen. Then why does she perform this marvelous act 

 of pollination? She does it to insure food for her 

 young. For, though the eggs were laid in the ovary, 

 unless the ovules were properly fertilized they would 

 wither, would not develop; so the young caterpillars 

 would perish. A> ii is, the hairy tentacles, surrounding 

 and rubbing against the pollen-mass under her head, 

 take oft' some of the grains of pollen, and these are left 

 in the stigmatic chamber when she thrusts her proboscis 

 and tentacles therein. 



And what is I he sequence of this act? The pollen in 

 due time fertilizes the ovules; these begin to develop, 

 and at this stage may be likened to newly formed 

 garden peas in the pod. Xo one needs to be told that 

 these young peas are more tender, more succulent than 

 the fully mature pea. -lust as these ovules are forming, 

 the moth egg which is beside them hatches, and the little 

 caterpillar finds awaiting him a breakfast of new peas. 

 As the seeds develop, the larva grows; the two mature 

 together. About the time the seed-pod is ready to burst 

 open the larva bores its way out, descends the plant to 

 the ground, burrows several inches below the surface, 

 spins a silken cocoon intermixed with earth, there to 

 spend the remainder of the summer, the fall and winter, 

 awaiting the opening of the yucca flower the next sum- 

 mer, then to emerge to repeat the story, a series of acts 

 as yet unaccounted for. 



Has the question occurred to you, what benefit is 

 the plant to derive if the insect eats all the seed? 



