INSECTS AND FLOWERS 231 



younger stage, the stigma comes into contact with the 

 same part of the insect's body and cross-pollination re- 

 sults. The style of the pistil bends down after pollina- 

 tion ; but if this should not take place, owing to no insect 

 having visited the flower, it remains erect until the 

 anthers shed their pollen upon the stigma. In the early 

 stage of the flower, therefore, the conditions favour cross- 

 pollination ; in the later stage, self-pollination is still 

 possible. 



The fact that the flgwort blooms exhale an unpleasant 

 odour lends support to our belief that the scents of flowers 

 are appreciated by insects. Wasps, as everyone knows, 

 have a liking for strong meats, although they consume a 

 certain amount of sweet food as well. When they visit 

 the figwort they are perhaps a little disappointed to find 

 nectar instead of carrion ; but they solace themselves with 

 the sugary fluid, and incidentally serve the flower by pro- 

 moting its cross-fertilisation. We see, therefore, that 

 while the delicate perfumes of many flowers are calculated 

 to charm such insects as butterflies, moths, and bees, the 

 strong odours of others are peculiarly attractive to certain 

 flies and beetles which revel in the products of decay. 

 Many large tropical flowers attract carrion-feeding insects 

 in this way. Both in their coloration (" livid spots, violet 

 streaks, and red-brown veins on a greenish or fawn-coloured 

 background ") and in the disgusting odours which they 

 distil, they reproduce the evidences of putrefaction. By 

 such means the huge tropical birthworts (Aiistolochia) 

 lure flies into their cavernous corollas through a narrow 

 opening beset with hairs directed inwards. Although 

 entrance is easy, immediate return is impossible. The 

 flies are held in durance until the pistil passes maturity 

 and the stamens ripen and shed their pollen. Then the 

 hairs of the tube shrivel up and release the prisoners, 



