Aphid-Eating Ladybugs Supplement Their Diet with Leafy Greens
Ladybugs are an important agricultural tool and help farmers by feeding on aphids, thereby controlling this serious agricultural pest. For this reason, learning which types of plants ladybugs eat, and how to keep these beneficial insects healthy, can be a great advantage for farmers.
Most animals have an appetite for five major nutrient groups: carbohydrates, fat, protein, sodium, and calcium. However, Todd Ugine, a research associate in the lab of John Losey, a professor of Entomology at Cornell University, has recently discovered a sixth appetite in aphid-eating ladybugs: sterols. Ladybugs feed almost exclusively on aphids, a smaller insect almost devoid of the essential nutrient sterols (a well-known example of which is cholesterol). Since ladybugs can not get the sterol nutrients they need from aphid consumption, they will seek out sterol-rich leaves to eat.
Ugine conducted an experiment with seven different ladybug species to examine their relationship with sterols. He designed different treatment groups: males and females who were either exclusively carnivorous (eating only aphids) or omnivorous (eating both aphids and sterol-rich leafy greens).
“Generally, all the beetles survived very well but when we looked at the total number of eggs laid and the percentage of eggs and females that were viable, that’s when we saw a huge effect,” Ugine told CALS of the study’s conclusion. He found that females mated with an omnivorous male laid more eggs and more of those eggs hatched than compared to females mated with exclusively carnivorous males. In conclusion, ladybugs that consume sterols through leafy-greens in addition to aphids have more viable offspring and ultimately greater fitness.
Future research in this field will investigate sterol taste receptors, and if lacewings and hoverflies — additional species that feed on aphids — will also search out sterol sources when deficient.
Read more about the study in CALS online news.