BEES 203 



lar reason the males of any species of bee may not visit the same flow- 

 ers as the females, though the attraction of the female may largely 

 influence their course, in which respect they exhibit quite human senti- 

 ments. It would, of course, be in vain to look for the males of Bombus 

 and Halictus on the flowers of spring, since they do not appear until 

 mid-summer. In the case of dioecious plants, or plants in which the 

 sexes are on different individuals, the bees visiting the staminate flow- 

 ers are more numerous and are sometimes widely different from those 

 visiting the pistillate. The common sumach is a good example. In- 

 deed the bees visiting a flower in its early stages may differ from those 

 visiting it in its later stages. Again the visitors to a flower may differ, 

 both in number and kind, in different seasons. 



The depth at which the nectar is concealed is another most im- 

 portant factor in controlling the visits of bees. In some flowers it is 

 fully exposed on a flat surface where it is accessible to all insects; in 

 others it is at the bottom of a slender tube, where it can be reached only 

 by the larger moths. The familiar fable of the crane and the fox is 

 constantly illustrated among flowers. As a matter of fact, bumblebees 

 and butterflies avoid rotate, flat flowers containing little nectar, since 

 their long tongues do not permit them to suck easily on such a surface. 

 On the other hand, it would be useless to look for the smaller bees with 

 short tongues on the larkspurs and clovers, for the nectar is quite beyond 

 their reach. 



As we take our leave of the oligotropic bees it may be inquired if 

 there are any other insects, which visit only one species of flower. There 

 are many others, especially among butterflies and moths. The flag 

 beetle (Mononychus vulpeculus) passes its entire life on the blue flag 

 (Iris versicolor) . This small weevil feeds both on the pollen and nectar 

 and sometimes gnaws the flower-leaves badly. The eggs are laid in the 

 young seed capsules, where the larvae feed on the ripening seeds. Both 

 the adult beetles and larvae are supported at the expense of the blue 

 flag. The legitimate pollinators are bees and while the flag beetle may 

 rarely effect pollination it does far more harm than good. This symbi- 

 otic relation is a benefit to the insect, but an injuiry to the plant. 



Two slender metallic-hued beetles (Donacia rufa and Donacia pisca- 

 trix) find very comfortable quarters within the flowers of the yellow 

 water lily, where they idle away much time drinking nectar and eating 

 pollen. They lay their eggs on the leaves and the larvae burrow in the 

 stems. As in the case of the flag beetle this arrangement is evidently 

 more to the advantage of the beetles than of the plants. 



The night-blooming yucca, or Spanish bayonet, which flourishes 

 throughout the southern states,' is pollinated exclusively by a small noc- 

 turnal moth. The larvaa of the moth live in the seed-capsules. Thus 

 both plant and moth are reciprocally dependent on each other, and the 

 destruction of the one would be followed by the disappearance of the 

 other. But in most instances the insect receives the greater benefit. 



