Chap. IY.] NATUKAL SELECTION. 117 



length of the proboscis, &c, too slight to be appreciated 

 by us, might profit a bee or other insect, so that certain 

 individuals would be able to obtain their food more 

 quickly than others ; and thus the communities to which 

 they belonged would nourish and throw off many swarms 

 inheriting the same peculiarities. The tubes of the 

 corolla of the common red and incarnate clovers (Trifo- 

 lium pratense and incarnatum) do not on a hasty glance 

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

 suck the nectar out of the incarnate clover, but not out 

 of the common red clover, which is visited by humble- 

 bees 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 humble-bees. 

 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 country 

 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 humble-bees were to become rare in 



