

INSECTS IN RELATION TO PLANTS 



225 



Insect Pollenizers. The great majority of entomophilous flowers 

 are pollenized by bees of various kinds; the apple, pear, blackberry, 

 raspberry and many other rosaceous plants depend chiefly upon the 

 honey bee, while clover cannot set seed without the aid of bumblebees 

 or honey bees, assisted by wild bees such as Tetralonia and Melissodes. 

 Lilies and orchids frequently employ butterflies and moths, as well as 

 bees, and the milkweed is adapted in a remarkable manner for pollination 

 by butterflies, moths and some wasps, as was described. Honeysuckle, 

 lilac, azalea, tobacco, Petunia, Datura and many other strongly scented 

 and conspicuous nocturnal flowers attract for their own uses the long- 

 tonged sphinx moths (Fig. 263); the evening primrose, like milkweed, 

 is a favorite of noctuid moths. 

 Umbelliferous plants are pollen- 

 ized chiefly by various flies, but 

 also by bees and wasps. Pond 

 lilies, golden rod and some other 

 flowers are pollenized largely by 

 beetles, though the flowers exhibit 

 no special modifications in relation 

 to these particular insects. It is 

 noteworthy that pollination is per- 

 formed only by the more highly 

 organized insects, the bees head- 

 ing the list. 



Of all the insects that haunt the 

 same flower, it frequently happens 

 that only a few are of any use to the 

 flower itself; many come for pollen 



only; many secure the nectar illegitimately; thus bumblebees puncture 

 the nectaries of columbine, snapdragon and trumpet creeper from the 

 outside, and wasps of the genus Odynerus cut through the corolla of 

 Pentestemon l&mgatus, making a hole opposite each nectary; then there 

 are the many insects that devour the floral organs, and the insects which 

 are predaceous or parasitic upon the others. In the Iris, according to 

 Needham, two small bees (Clisodon terminalis and Osmia distincta) are 

 the most important pollenizers, and next to them a few syrphid flies, 

 while bumblebees also are of some importance. The beetle Trichius 

 piger and several small flies obtain pollen without assisting the plant, 

 and Pamphila, Eudamus, Chrysophanus and some other butterflies 

 succeed after many trials in stealing the nectar from the outside (Fig. 



FIG. 263. Protoparce sexta visiting flower 

 of Petunia. Reduced. 



15 



