232 A BOOK OF INSECTS 



well dusted with pollen, which they carry to another 

 flower. 



Very similar is the treatment accorded to its insect 

 visitors by the familiar wild arum, or cuckoo-pint [Arum 

 macuhtum). The flower spike of this plant, called the 

 spadix, is enveloped by a large sheathing bract, or spathe. 

 The spadix ends in a purple club, and bears the flowers 

 clustered upon its lower part. They comprise abortive, hair- 

 like flowers ; anthers or male flowers ; and pistils or female 

 flowers — this being the order of their arrangement from 

 above downwards. Insects, especially a small midge known 

 as Psychoda phalcenoides, are attracted by the purple club 

 of the spadix and the strong odour of the inflorescence. 

 The hair-like flowers radiate downwards, and allow the 

 insects to creep into, but not to escape from, the cham- 

 bered portion of the spathe. The female flowers mature 

 first, and receive pollen brought by the insects from 

 another inflorescence. Later, the anthers or male flowers 

 mature, and the midges get dusted with pollen. Finally, 

 the abortive hair-like flowers shrivel up, the spathe begins 

 to wither, and the midges make good their escape. If 

 any of them fly to another arum, they will help to cross- 

 pollinate its female flowers. It is not uncommon to find 

 several hundreds of these tiny midges in the cavity of 

 a single spathe. 



In some flowers the pollen is bound up into convenient 

 masses, and these are torn away bodily by the visiting insect 

 and carried to another bloom. Many of the orchids, for 

 instance, are really elaborate contrivances to secure cross- 

 pollination in this way. In our own early purple orchis 

 (Oi'chis mascula) there are six perianth leaves, five of which 

 form a kind of hood over the essential organs ; while the 

 sixth is a broad lip, called the labellum, which serves as an 

 alighting platform. The labellum is also continued back- 



