nsects damage plants in several ways, one of which is to pierce plant tissues with their sharp mouth parts and suck out the plants' fluids. Sucking insects often secrete unused juices, sometimes called “honeydew,” making the leaves and stems of plants sticky. Diseases can enter the plants through the openings made by the insects, and some insects inject toxins into the plants. Every gardener is likely to battle the most common sucking insects at least once.
On the other hand some insect suck flower juice they help in pollination and honeybee produce honey by sucking the juice from insect.
In these picture three insect are sucking one flower which seems pretty beautiful.
(Butterfly/Moth top, Beetle bottom left, Spider bottom right)
Insects are great at polinating flowers and other plants!