Tumbling Flower beetles

Tumbling Flower beetles, (TFBs) always reminds the BugLady of a flea on a flower. Tumbling Flower beetles are small, active, generally dark, caraway-seed-shaped beetles in the Tumbling Flower beetle family, Mordellidae, a family with some very fine genus names like Mordellistena, Hoshihananomia, and Yakuhananomia.

These beetles are basically black and about 1/4-inch long. They are wedge shaped with the tail coming to a point. M. atrata is almost solid black except for the base of the tail which show shows silvery pubescense. M. marginata is very similar but shows a variety of irregular silvery pubescent patterns on the pronotum and elytra. The hind legs are flattened and have an enlarged femur which they use to kick when they are in hard surface.

This kicking gives them the name of tumbling flower beetles when they bounce erratically in a net. There are several other members of the genus Mordella. The largest genus in the family is Mordellistena which are generally smaller and seldom as common. They may be patterned or plain and come in a variety of colors from black, yellow, brown and reddish.

Life Cycle: The tumbling flower beetle has one generation per year, the adults emerging in spring around the same time as stem weevils. The adults feed mostly on pollen and the females insert their eggs just under the epidermis in sunflower petioles. Early planted fields normally host the most larvae. Stalk dissections in Kansas suggest that this is possibly the most abundant of all stem-boring insects in wild H. annuus where as many as 30 or 40 larvae may reside in the same plant, all distributed in different branches.

They are not nearly as abundant in cultivated sunflowers where stem weevils seem to predominate, possibly due to the lack of branches that seem to be their preferred niche within the plant. Similar to the cerambycid larvae that also inhabit the pith core of the stalk, they are highly aggressive toward one another and do not tolerate the presence of conspecifics.

Interestingly, in cultivated sunflowers, larvae are found in the matrix of the main stalk, not in pith core, possibly because they are unable to compete with the much larger cerambycid larvae for this niche.

Habitat and Food Source: Adults apparently feed on pollen of many flowers. They are often found on umbelliferous flowers and composites and can be abundant in some circumstnaces. The adults are most often seen in the spring. Several species may occur together.

Damage: Tumbling flower beetles feed mostly on pollen but also chew flowers. Damage is usually minor.

Management: There is no economic injury level for tumbling flower beetles in sunflowers, but the larvae may contribute to stalk damage collectively with other insects. They are easily distinguishable from most other boring larvae in sunflower stalks and should not be mistaken for species of greater economic significance.