|Long-horned Locust Borer Beetle (a yellowjacket mimic) on Goldenrod
|Chafer Beetles on Maple-leaf Viburnum
|Margined Leatherwing Soldier Beetles mating while pollinating Dogbane
Some flowers, often from ancient lineages such as magnolias depend on beetles as their primary pollinators. Such flowers are referred to as cantharophilous flowers and beetle pollination is referred to as cantharophily. Some flowers that have beetles as their primary pollinators include some magnolias, lizard's tail, sassafras some palms, cycads, and I believe sessile trillium.
|Click Beetles inside a Sessile Trillium flower
So beetles may not be the most obvious pollinators, or even the prettiest or best, but they are vital for the pollination of many of our plants. They may even have ulterior motives for visiting flowers, to eat the pollen or sex, but they are important, if under appreciated none the less.
|Two different beetles on a Swamp Rose.