Other Pollinators: Beetles


Beetle Much has been written about the importance of butterflies and bees to the pollination process. However, many of us never considered the importance of beetles to this essential task. It makes sense, considering the fact that about 450,000 species of beetles are known, comprising about 40 percent of all known insects.

Of the world’s almost 350,000 flowering plants, it is thought that beetles are responsible for pollinating close to 90 percent of them.

The First Pollinators

The first beetle-like organisms in the fossil record date back to the Permian Period, roughly 270 million years ago. True beetles – those that resemble our modern-day beetles – first appeared about 230 million years ago. Beetles were already in existence before the breakup of the supercontinent Pangaea, and they survived the K/T extinction event thought to have doomed the dinosaurs. How have beetles survived for so long, and withstood such extreme events? As a group, beetles have proved remarkably adept at adapting to ecological changes.

Fossil records show that beetles were abundant during the Mesozoic (about 200 million years before present). Beetles were flower visitors of the earliest angiosperms. Many present-day beetle pollination associations like that of Magnolia, a primitive woody angiosperm, have ancient evolutionary origins.

Beetles were among the first insects to visit flowers and they remain essential pollinators today.

What is cantharophily?

Beetle cantharophily Very few plants are primarily pollinated by beetles. Those that are dependent on beetles are called cantharophilous plants. 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 goldenrod 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. This is why they are sometimes called “mess and soil” pollinators.

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.

Beetle Flowers

The flowers that are visited by beetles are typically:

•  Bowl-shaped with sexual organs exposed
•  White, to dull white or green
•  Strongly fruity
•  Open during the day
•  Moderate nectar producers
•  May be large solitary flowers (i.e. magnolias, pond lilies)
•  May be clusters of small flowers (goldenrods, Spirea)

Features of Beetle Pollinated Plants

•  Flowers dull-coloured or white
•  Nectar guides, nectar and nectaries often absent
•  Radially symmetrical
•  Strong fruity or yeasty, fermented odors
•  Pollen or food bodies as reward to pollinators
•  Often use heat as a reward

Beetle Anatomy

Beetle Anatomy Diagram •  Skeleton: Beetles don’t have bones and an internal skeleton like we do. They have an exoskeleton that is like a large shell. It protects them and gives them shape. Tiny hairs called “setae” on the outside of the exoskeleton help improve the beetle’s perception of touch and sound.

•  Eyes: Beetles have “compound eyes.” Each eye is made up of many units called “ommatidia”. There can be thousands of ommatidia in a single beetle eye. Through the ommatidia, beetles see in patterns of light and dark dots.

•  Antennae: Antennae are very important to beetles, as they provide constant information about touch, smell and taste. Beetles use taste and smell eceptors on their antennae to locate food and also to identify pheromones.

•  Mouthparts: Mountain pine beetle need strong mouthparts to be able to chew through bark and phloem. Their mouthparts move in a cutting motion like scissors.

•  Thorax: The thorax is the middle body region – between the head and the abdomen – that serves as an attachment point for the legs and wings. This is where the heart is located which pumps blood toward the front of the body. Blood does not circulate through vessels, but passes freely between and around body organs. The thorax itself is composed of 3 segments, with a pair of legs located on each segment and 2 pairs of wings found on the second and third segment. The thorax is where the muscles are located that help the beetle walk, jump and fly.

•  Legs: Adult beetles have 6 legs. Each of the segments of the thorax bears 1 pair of legs. The legs are jointed, and the last segment of the leg bears a small claw.

•  Wings: The beetle has two pairs of wings found on the second and third segment of the thorax. One pair is the hard-shelled outer wings called the “elytra”. These are not used for flying, but to protect the beetle’s flying set of wings and its body as it crawls through narrow passages and tunnels in a tree. The second set of wings is membranous or see-through, and is folded under the elytra when not in use.

•  Abdomen: The abdomen is the posterior or last of the three body regions in the mountain pine beetle. It is the biggest body part and is composed of 11 segments. The abdomen holds the beetle's digestive system and reproductive organs, and is also where beetles breathe! Beetles don’t have lungs like mammals do – instead they breathe through a series of holes in their abdomens called “spiracles.”

Basic Facts About Beetles

Beetles inhabit nearly every ecological niche on the planet. This group includes some of our most beloved bugs, as well as our most reviled pests. Here are 10 fascinating facts about beetles, our largest insect order.

Beetles are the largest group of living organisms known to science, bar none. Even with plants included in the count, one in every five known organisms is a beetle. Scientists have described over 350,000 species of beetles, with many more still undiscovered, undoubtedly. By some estimates, there may be as many as 3 million beetle species living on the planet. The order Coleoptera is the largest order in the entire animal kingdom.

You can find beetles almost anywhere on the planet, from pole to pole, according to entomologist Stephen Marshall. They inhabit both terrestrial and freshwater aquatic habitats, from forests to grasslands, deserts to tundras, and from beaches to mountaintops. You can even find beetles on some of the world's most remote islands.

Research has shown that beetles are capable of seeing color, but they mainly rely on their sense of smell for feeding and finding a place to lay their eggs.