Beetles are always included in lists of pollinators. In fact, it is likely beetles were the first pollinators, moving pollen between flowers in some of the earliest flowers.
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| beetle on a daisy flower |
Beetles are insects in the order Coleoptera, the largest of all orders, with about 400,000 species. As flower-visitors, they are looking for food, eating pollen, chewing petals, drinking nectar. Pollen adheres to their bodies and then brushes onto the flower's stigma to self-pollinate or be carried to the next flower for cross-pollination.
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| beetle in a rose flower |
Of the thousands of species of beetles, only some pollinate. Families of beetles that pollinate include Anthicidae (ant-mimic beetles), Bostrichidae (auger beetles), Buprestidae (jewel beetles), Cantharidae (soldier beetles), Cerambycidae (long-horned beetles), Cetoniidae (flower chafers), Chrysomelidae (leaf beetles), Cleridae (checkered beetles), Coccinellidae (ladybugs/ladybird beetles), Corylophidae (minute hooded beetles), Cryptophagidae (silken fungus beetles), Curculionidae (weevils), Elateridae (click beetles), Histeridae (clown or hister beetles), Hybosoridae (scavenger scarab beetles), Hydrophilidae (water scavenger beetles), Lagriidae (long-jointed beetles), Mordellidae (tumbling flower beetles), Nitidulidae (sap beetles), Ptiliidae (featherwing beetles), Rutelidae (shining leaf chafers), Scarabaeidae (scarabs), Staphylinidae (rove beetles), Tenebrionidae (darkling beetles), and probably several more. Numerous as they look, these are just a few of the estimated 200 families of beetles.
Likewise, many plant species are beetle-pollinated, but especially plants in the custard apple family (Annonaceae), palms (Arecaceae), cyclanths (Cyclanthaceae), proteus family (Proteaceae), magnolia family (Magnoliaceae), nutmeg family (Myristicaceae), chocolate family (Sterculiaceace), and dipterocarps (Dipterocarpaceae), which are mostly tropical families.
Beetle pollination occurs in temperate regions, but, there, it is overshadowed by bee- and butterfly-pollination, in research studies, at least. In the tropics, a substantial number of plants, 20-40% as measured in studies of tropical ecosystems, rely on beetles as their chief pollinators. Some are important crops, such as sour sop and relatives (Annonaceae), and the palms (Arecaceae).
Beetle pollinated flowers are quite diverse, but some flower characteristics occur a lot. Often beetle-pollinated flowers have a lot of pollen so the hungry beetles get plenty to eat and still pollinate. They frequently have reinforced tissues to protect the important flower parts from damage as the beetles feed. Bowl-shaped flowers are common.
Many beetle-pollinated flowers have strong scents. Depending on the species, those scents can be fruit-like, flowery, carrion-like, fishy, nauseating, like feces, and more. Flower color ranges from reds and purples to yellows, pinks, and whites. Many beetles have color vision but nevertheless locate food mainly by scent. An unusual feature of many beetle-pollinated flowers is that the flowers are thermogenic, generating heat. This keeps the beetles more comfortable in chilly seasons or parts of the day, reduces their energy needs, mimics oviposition resources (a lot of beetle mating goes on when they meet in a flower), and better disperses the flower's scents. Magnolias (there are more than 200 species of Magnolia) are a classical example of flowers adapted to beetle pollination. Two North American plants that rely on beetles for pollination are tulip trees (Liriodendron) and paw-paws (Asimina).
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| Magnolia |
Beetles are considered generalist pollinators, pollinating anything with an open enough flower for them to enter. That is probably over-simple. Recent studies of two beetle families and their associations with plants found strong patterns: some plant groups (families) are pollinated by beetles while the beetles ignore many other plant groups entirely; similarly some groups of plants have many species pollinated by related beetles and are diverse in their flower shapes and pollination details. These patterns suggest a long and important relationships between the plants and the beetles.
The Mediterranean region of Europe has a 'poppy guild' of early spring flowers, reddish and bowl-shaped like the classical poppy, that are pollinated by beetles. This group ("guild") includes a red anemone Anemone coronaria, a red buttercup Ranunculus asiaticus, and the tulip, Tulipa agenensis. as well as a red pheasant's eye (Adonis) and red horned poppy (Glaucium). Their flowers share a simple symmetrical shape, red-orange petals and a dark center. They have very little scent. These plants flower early in the spring, before most bees are flying, and attract many local beetles, especially scarabs (genus Amphicoma) which are effective pollinators. Dafni and coauthors further showed that the beetles were more attracted to red flowers than other colors and to flowers with black centers over red flowers generally. This guild is found in Israel and across the southern edge of Europe and northern Africa, but not very far north into Europe.
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| common poppy, Papaver rhoeas |
Some plants pollinated by beetles have evolved complex iteractions. Many waterlilies (
Nuphar,
Nymphaea, and the giant waterlily
Victoria link) attract beetles with their scents, sweet or musky or spicy in different species. The waterlily flower then closes, trapping the beetles inside for a few hours or overnight. The beetles feed within the flower and have time to cover themselves in pollen. In the morning the flower reopens, the beetles escape, and another flower lures the pollen-covered beetles with its enticing scent.
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| water lily Nymphaea |
Some beetle-pollinated flowers provide small nutritive tissues that apparently have evolved to feed beetles, thus attracting more of them,
Calycanthus, sweetshrub, also called Florida allspice, is an example.
Many times, you will see beetles walking across open groups of small flowers. These let the beetles spread pollen. Examples are umbels, like dill (Anethum graveolens)and fennel (Foeniculum vulgare) in the dill family, Apiaceae, and the sunflowers (Helianthus), daisies (Leucanthemum and Bellis) and other composites in the sunflower family, Asteraceae.
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| composite, Mexican hat, Ratibida, with beetle |
Beetles are not generally considered good pollinators because they don't move far if they don't have to and can damage the flowers while feeding, but they are common and can make up in numbers what they lack in pollinating skills. Some pollinating beetles have heavy snouts, combs of setae (bristles) that catch pollen on their heads and legs, others appear quite fuzzy, not a characteristic you normally associate with beetles, but good for pollinating. The interaction of beetles with pollen is ancient, going back before flowering plants evolved; beetles are believed to have pollinated ancient cycads (
Cycladophyta) and gnetales (
Gnetophyta) 100 million years ago, as they do today. Beetle pollination likely drove the evolution of flowers (a flower is plant reproductive structure that is completely closed, protected from damage, the cones of gymnosperms have the same function but the ovary and the developing seeds are partially exposed) and leading to evolution of flowering plants and the world as we know it.
Spring is on the way. I am already looking for beetles in flowers. When I see a beetle in a flower, instead of going "aw, its a beetle not a bee," I'll linger to see if it moves pollen around.
Comments and corrections welcome.
References
Dafni, A., P. Bernhardt, A. Shmida, Y. Ivri, S. Greenbaum, C. O'Toole and L. Losito. 1990. Red bowl-shaped flowers: convergence for beetle pollination in the Mediterranean region. Israel Journal of Botany. 39: 81-92.
Fallon, C. 2020. Notes from the other orders: beetles as pollinators. Xerces Society for Invertebrate Conservation link Accessed 4/12/25.
Herrera, C. M. and J. C. Otero. 2021. Plant phylogcny as a major predictor of flower visitation by nitidulid beetles, a lineage of ancestral angiosperm pollinators. Journal of Pollination Ecology. 29 (14): 179-186. doi: 10.26.26786/1920-7603(2021)636, (open access)
Muinde, J. and D. M. Katumo. 2024. Beyond bees and butterflies: the role of beetles in pollination system. Journal for Nature Conservation. 77: 126523. (9 pages)
Paz, F. S., C. E. Pinto, R. M. de Brito, V. L. Imperatriz-Fonseca, and T. C. Giannini. 2021. Edible fruit plant species in the Amazon forest rely mostly on bees and beetles as pollinators. Journal of Economic Entomology. 114 (2): 710-722.
Peris, D., C.c. Labandeira, E. Barrón, X. Delclós, J. Rust and B. Wang 2020. Generalist pollen-feeding beetles during the mid-Cretaceous. iScience. https://doi.org/10.1016/j.isci.2020.100913 link (open access)
Proctor, M., P. Yeo, and A. Lack. 1996. The Natural History of Pollination. Timber Press, Portland Oregon.
Sabatinelli, G., J. Eberle, S. Fabrizi, and D. Ahrens. 2020. A molecular phylogeny of Glaphyridae (Coleoptera: Scarabaeoidae): evolution of pollination and association with 'poppy guild' flowers. Systematic Entomology. 45: 838-848. DOI: 10.1111/sysen.12429 (open access)
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