Study Explores How Flower-Eating Katydids Pick Their Meals
By Ed Ricciuti
The flash with which flowers attract pollinators does not necessarily attract insects that like to nosh on them, say researchers at the National University of Singapore.
When it comes to predicting the palatability of a flower to insects, there is more to it than meets the eye, according to researcher Ming Kai Tan and doctoral supervisor Hugh Tan, Ph.D., of the university’s department of biological sciences. Unlike the showy way flowers advertise for pollinators, they say “it is likely that physical traits and/or chemical contents are probably more important to florivores [insects that eat flowers] than visual clues.” In other words, as far as insects are concerned, just because a flower looks good does not mean it’s good to eat.
A new paper the researchers published in the Journal of Economic Entomology this month explores the relationship of different floral attributes and how they relate to florivory, the consumption of flowers by insects. Unlike often-studied herbivory, or leaf eating, florivory has gone largely unplumbed, although the new research suggests parallels between the two exist. The less matter remaining in leaves that have been dried in the laboratory, for example, the more herbivores like them, and the same, the paper reveals, is true of flowers. Not surprisingly, the less dry a leaf or flower is, the more tender it is, making it more palatable. At the same time, however, the researchers cautioned against over-broad generalizations because, for instance, some insects have adapted specializations for chewing on tough plants.
The research focused on the eating preferences of a katydid common in Southeast Asian scrublands, Phaneroptera brevi, which the scientists collected locally with a sweep net. During the experiments, the insects were offered, cafeteria style, samples of three weedy members of the Asteraceae family. Typically, what people generally call a “flower” in this group of 20,000 species is actually a composite of many small flowers, or florets, some tiny bumps tightly packed in a central disk, the others in petal-like rays around it. Think “daisy” or “sunflower” and you have the picture.
The Singapore study focused on traits in the ray florets, which turned out to better predict palatability than those in the disc. All in all, the research suggests that insects are most attracted to food that can be harvested easily with less energy spent in the process.
As in leaves, specific area and biomass of rays tended towards palatability, for good reason. The potency of a flower’s defenses, such as thicker cell walls and more fiber cells, that increase tissue concentration and mechanical strength, varies conversely with area. Since the greater the biomass the more food is available within a given time frame, say the researchers, “the amount of consumable biomass that will be accepted by the katydid is more important than visual display of the asterid species in predicting likelihood of florivory.”
Research such as that described in the paper could have important ramifications for agriculture and perhaps for control of noxious and invasive weeds. Study of flower traits related to insect feeding, says Ming Kai Tan, “can have applications in horticulture, where breeders might be interested in looking at traits of their varieties and cultures that are more resilient to flower feeders. Growing crops which are more resilient to flower feeders can be crucial to the yield, especially for fruit crops.”
Understanding traits that encourage florivory also may help weed control. Learning how flower feeders respond to weeds may reveal why some weeds are more persistent than others, potentially leading to new methods of combatting them.
Journal of Economic Entomology
Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.