(Beyond Pesticides, April 5, 2017) The tumbling flower beetle is the pollinator of the month for April. The tumbling flower beetle is the common name for Mordellidae, a family of beetles comprising over 1,500 species, 200 of which are found in North America according to the Field Guide to Beetles of California. Their common name is derived from the movement pattern they exhibit when disturbed. The beetles use their large rear legs to kick, jump, and tumble in an erratic pattern to the confusion of predators and the amusement of human observers.
The differentiation in this large family lends itself to near ubiquity. According to the Encyclopedia of Life, the tumbling flower beetle can be found on every continent except Antarctica. Texas A&M notes the individual species are not overly adapted to specific environments and a number of species frequently overlap within a single ecosystem.
Diet and Pollination
Beetles are frequently overlooked in the world of pollinators. According to the U.S. Department of Agriculture’s Forest Service, the tumbling flower beetle’s ancestors were some of the earliest insects to utilize flowers for food and habitat. In doing so, these ancient pollinators began an important collaboration between flowers and beetles which continues today. Mature tumbling flower beetles feed on the pollen of flowering plants. They pollinate as they feed, transporting pollen on their body from a previous flower to successive locations. Idaho State University notes that beetles play a more important role in the pollination of tropical regions than in temperate ones. Even so, there are approximately 50 native plant species in the U.S. and Canada which depend upon beetle pollination.
The large number of tumbling flower beetle species are unified by general appearance. Texas A&M describes the beetles as small, narrow, and wedge-shaped at just 1/4 inches long. Most species are black or dark brown but some are yellow or reddish and can exhibit thick bands, small stripes, and even spots. Their bodies are covered in fine hair which, in some species, becomes iridescent in sunlight. The tumbling action, for which the beetle is named, is caused by their jumping technique. They are equipped with large and strong rear legs for powerful jumping. Interestingly, they use a single leg of the rear pair to apply an uneven force to the ground and cause their body to both roll and somersault. According to the Encyclopedia of Life, the beetle uses this action to reposition its body for takeoff and may make successive tumbles until the correct position is achieved. Tumbling flower beetles are strong fliers but also frequently elect to tumble to the safety of ground from their perch.
The guidebook Attracting Native Pollinators notes that the life cycle of the tumbling flower beetle revolves around the flowers it pollinates. With the onset of spring, the beetles reach maturity and begin to mate. In most species, the females lay their eggs in the stalk and stems of those same flowers. There, the larvae will develop and feed until the following spring when they emerge and repeat the process. Some other species prefer to lay their eggs in decomposing wood where larvae play a limited role in recycling dead plant material. The tumbling flower beetle also plays an important ecological role as prey to other creatures. The article Bird predation and the host-plant shift by the goldenrod stem galler notes that downy woodpeckers and other birds eat tumbling flower beetle larvae. Adults are hypothesized to be prey to birds as well in A mordellid-meloid mimicry. Further, crab spiders are known ambush predators of a wide range of insects which frequent flowers.
Threats to Existence
The tumbling flower beetle family of species is currently thriving and is not listed on the International Union for Conservation’s Red List of Threatened Species. This means there is no evidence that the existence of the family is currently at risk. Even though the tumbling flower beetle is not in immediate danger, conservation efforts to protect its future should not be ignored. According to Kansas State University and Texas A&M, the tumbling flower beetle does little to no damage to crops and is not considered an agricultural pest. However, its larvae do bore into stalks and may be grouped with other stalk-boring insects which collectively cause crop damage. The crops which house the tumbling flower beetle larvae may be treated with pesticides targeting more destructive insects to the detriment of tumbling flower beetle populations. However, the stem-boring habit of the larvae generally protects it from non-systemic pesticides.
How to Protect the Species
There are steps that can be taken to ensure that the tumbling flower beetle continues to thrive. Noted favorite plants in the Field Guide to Beetles of California are buckwheat and sunflowers. Texas A&M suggests the composite and umbelliferous flower families are also popular. Planting these preferred varieties of flowers is a great way you can support the tumbling flower beetle. They will use the plants’ stems to host their larvae and their pollen as a food source. The females will insert their eggs beneath the skin on stems. According to Kansas State University, as many as 40 larvae may be distributed throughout the plant in this way. Avoiding the use of pesticides is paramount in protecting beneficial pollinators in your area. Tumbling flower beetles can be exposed by interacting with plants, soil, or air that have been subjected to pesticides. You should be aware of the chemicals used in your gardening solutions and avoid buying products that that contain neonicotinoids, a class of chemicals linked to pollinator declines. For more information on the impact pesticides have on non-target organisms read Beyond Pesticides’ report on Bees, Birds, and Beneficials, which can be found here. Switching to organic means of pest control around your home and garden is the best way to protect the health of pollinator populations in your community. For more information on how you can get involved in pollinator conservation throughout the nation, see Beyond Pesticides BEE Protective webpage.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.