NATURAL SELECTION 1497 



would flourish and throw off many swarms inheriting 

 the same peculiarities. The tubes of the corolla of 

 the common red and incarnate clovers (Trifolium 

 pratense and incarnatum) do not on a hasty glance 

 appear to differ in length; yet the hive-bee can easily 

 suck the nectar out of the incarnate clover, but not 

 out of the common red clover, which is visited by 

 bumblebees alone; so that whole fields of the red 

 clover offer in vain an abundant supply of precious 

 nectar to the hive-bee. That this nectar is much liked 

 by the hive-bee is certain; for I have repeatedly seen, 

 but only in the autumn, many hive-bees sucking the 

 flowers through holes bitten in the base of the tube 

 by bumblebees. The difference in the length of the 

 corolla in the two kinds of clover, which determines 

 the visits of the hive-bee, must be very trifling; for 

 I have been assured that when red clover has been 

 mown, the flowers of the second crop are somewhat 

 smaller, and that these are visited by many hive-bees. 

 I do not know whether this statement is accurate; nor 

 whether another published statement can be trusted, 

 namely, that the Ligurian bee, which is generally 

 considered a mere variety of the common hive-bee, 

 and which freely crosses with it, is able to reach and 

 suck the nectar of the red clover. Thus, in a coun- 

 try where this kind of clover abounded, it might be 

 a great advantage to the hive-bee to have a slightly 

 longer or differently constructed proboscis. On the 

 other hand, as the fertility of this clover absolutely 

 depends on bees visiting the flowers, if bumblebees 

 were to become rare in any country, it might be a 

 great advantage to the plant to have a shorter or more 



