According to findings in fossils, beetles (order Coleoptera) first pollinated cycads. Coleoptera were on earth and visiting flowers when angiosperms first appeared and were at work a good 150 million years ago. Bees appeared a few million years later (30 to 50 million years according to some estimates). Many beetles today still prefer to pollinate the descendants of the early angiosperms. Beetles that pollinate these flowers are called Coleopteran pollinators, and the flowers that depend on them are called cantharophilous flowers. The process of beetle pollination is called cantharophily.
Cantharophilous fowers share several common characteristics. Typically the flowers are bowl-shaped with exposed sexual organs; they are white to dull white or green and have a strong fruity odor. Structure is usually simple, with no distinction between the petals and sepals. A moderate amount of nectar may be produced by these day-opening flowers. The flowers are usually radially symmetrical and may be large and solitary, such as magnolias and water lilies, or they may be clusters of small flowers, like golden rod and composites.
Descriptions of beetle pollination sound repugnant to us clean-loving humans. The beetles eat their way through petals and other parts of the flower. Then they defecate within the flowers and roll around in it as they relish the pollen inside. Ugh! This is why they are sometimes called “mess and soil” pollinators.
Scientists have now divided plants into groups called monocots, eudicots, and basal angiosperms. Monocots have the same definition we learned in grade school science. In a previous article for Dave’s Garden, “Monocots and Whaticots? Eudicots?” (March 5, 2014), I discussed the particulars of these three classifications. The basal angiosperms are most frequently pollinated by beetles.
The basal angiosperms include Amborellales, Nymphaeales (waterlilies and relatives), Austrobaileyales (some flowering woody plants such as Illicium), Chloranthales, and Magnoliids. The Magnoliids include such familiar plants as magnolias, pawpaws, pipevine, redbay, camphor tree, sassafras, and the wild lizard’s tails found in wet places. Flowers from these lineages share certain primitive features.
While some beetle-pollinated plants produce moderate amounts of nectar, most of the basal angiosperms lack nectar guides, nectar, and nectaries so important to bees and butterflies. Some basal angiosperms are thermogenic and offer the additional reward of heat. Heat may help to volatize the scent of the flower, or it may help the sluggish beetle which cannot generate much heat of its own.
Pollinating beetles are not searching for nectar; for them the reward is pollen. Beetles believed to provide pollination include members of several beetle families: soldier, jewel, blister, long-horned, checkered, tumbling flower, scarab, sap, false blister, rove, and many other types of beetles.
The more we learn about the important tasks of pollinators in general, the more we become aware of how important every little bee, butterfly, and beetle is to the welfare of the earth and its inhabitants. We become more aware of the importance of not using insecticides, and we learn to nurture and treasure (almost) every little insect. After all, they work hard for us. Life without them would be vastly different.
Thumbnail image courtesy of BugFiles and DG member Magpye. The magnolia image is my own.