Fragrant flowers with well developed nectaries are an adaptation for

Fragrant flowers with well-developed nectaries are an adaptation for Entomophily.
Some flowers possess pleasant odour and attractive colours for Entomophily.
Entomophily or insect pollination is a form of pollination whereby pollen of plants is distributed by insects.
Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns leading to rewards of pollen and nectar; they also have an attractive scent which in some cases mimics insect pheromones.