422 HABITS OF INSECTS CHAP. XL 



this must often occur, as, according to M. Brisout, 

 " many of the species affect only one kind of plant." * 



It must not be supposed from these several statements 

 that insects strictly confine their visits to the same 

 species. They often visit other species when only a 

 few plants of the same kind grow near together. In a 

 flower-garden containing some plants of (Enothera, the 

 pollen of which can easily be recognised, I found not 

 only single grains but masses of it within many flowers 

 of Mimulus, Digitalis, Antirrhinum, and Linaria. 

 Other kinds of pollen were likewise detected in these 

 same flowers. A large number of the stigmas of a plant 

 of Thyme, in which the anthers were completely aborted, 

 were examined ; and these stigmas, though scarcely 

 larger than a split needle, were covered not only with 

 pollen of Thyme brought from other plants by the bees, 

 but with several other kinds of pollen. 



That insects should visit the flowers of the same 

 species as long as they can, is of great importance 

 to the plant, as it favours the cross-fertilisation of 

 distinct individuals of the same species ; but no one 

 will suppose that insects act in this manner for the good 

 of the plant. The cause probably lies in insects being 

 thus enabled to work quicker ; they have just learnt 

 how to stand in the best position on the flower, and how 

 far and in what direction to insert their proboscides.f 

 They act on the same principle as does an artificer 

 who has to make half-a-dozen engines, and who saves 

 time by making consecutively each wheel and part for 

 all of them. Insects, or at least bees, seem much in- 

 fluenced by habit in all their manifold operations ; and 



* As quoted in ' American Nat.' conclusion -with respect to the 



May 1873, p. 270. cause of insects frequenting as 



t Since these remarks were long as they can the flowers of the 



written, I find that H. Miiller has same species : ' Bieiien Zeitung,' 



come to almost exactly the same July 1876, p. 182. 



