438 HABITS OF INSECTS. CHAP. XI 



those of most species of Salvia, of Trifolium pratense, 

 Phaseolus multijiorus, &c., will more or less completely 

 fail to produce seeds if the bees confine their visits 

 to the perforations. The perforated flowers of those 

 species, which are capable of fertilising themselves, 

 will yield only self-fertilised seeds, and the seedlings 

 will in consequence be less vigorous. Therefore all 

 plants must suffer in some degree when bees obtain 

 their nectar in a felonious manner by biting holes 

 through the corolla ; and many species, it might be 

 thought, would be thus exterminated. But here, as 

 is so general throughout nature, there is a tendency 

 towards a restored equilibrium. If a plant suffers 

 from being perforated, fewer individuals will be 

 reared, and if its nectar is highly important to the 

 bees, these in their turn will suffer and decrease in 

 number ; but, what is much more effective, as soon as 

 the plant becomes somewhat rare so as not to grow 

 in crowded masses, the bees will no longer _be stimu- 

 lated to gnaw holes in the flowers, but will enter 

 them in a legitimate manner. More seed will then be 

 produced, and the seedlings being the product of 

 cross-fertilisation will be vigorous, so that the species 

 will tend to increase in number, to be again checked, 

 as soon as the plant again grows in crowded masses. 



