ENTOMOPHILOOS FLOWeRS 133 



insects forget their temporary incarceration because of 

 the feed of honey which they get at the bottom of the 

 perianth cavity. Moreover, when the stamens have 

 passed maturity a kind of lid falls over the mouth 

 of the perianth-tube, which discourages insects from 

 entering it. There is then no honey to ailure insects, 

 nor pollen-grains for them to carry to other flowers. 

 Several species of Arum and other species of the 

 AracecB family have a similar pitfall arrangement, 

 not in their perianth, but in their s'pathe, and they 

 are also protogynous, like Aristolochia. The flowers 

 of neem have a sort of pit- 

 fall arrangement. They 

 are protandrous with a 

 sweet aroma. The fila- 

 ments form a hollow 

 column or tube with ten 

 imbricated limbs, and at Fig. ..7.-Poiiinia (/») of AsciepUs 



curassavica attached to the leg of a 

 the mouth of the tube ButterHy by dips (c) (after Knuth) 



Stand ten anthers at a 



higher level than the included stigma. The tube 

 is lined internally with hairs pointing downwards. 

 Small flies or midges are found within the flowers, 

 and they are the pollinating agents. But the pro- 

 tandrous condition is so slight, and the flowers so 

 dull-coloured, that self-pollination is also possible, 

 and does take place. 



9. Pinch-trap Flowers. — These flowers are pro- 

 vided with peculiar clips, to each of which two pollinia 

 are attached. The clips grasp the proboscis, claws, or 

 bristles of insect-visitors firmly, and are forcibly torn 

 away by the insects when they feel themselves held fast 

 (fig. 117). The insects, with the pollinia thus fastened 

 to their body, thrust them into the stigmatic cavity 

 unknowingly and unintentionally. Several .^jc/^m- 



