Okayama University demonstrates that flies die within seven days of exposure when caffeine used as an insecticide

Doctoral Student Shine Shane Naing (Myanmar), Professor Takahisa Miyatake and their colleagues at Okayama University's Graduate School of Environmental, Life, Natural Science and Technology have shown that common green bottle flies (Lucilia sericata; Order: Diptera) die within seven days after they consumed sugar water containing caffeine at 0.5% or a higher concentration. Depending on how caffeine is used, the findings are expected to contribute to the development of innovative insecticides.

Miyatake said, "We found that caffeine administered as a solution in sweet sugar water had an insecticidal effect on flies. The results of this study, led by a Myanmar student who came to Japan with support from JICA and government funds, demonstrated the effectiveness of caffeine. Depending on its application, this may lead to its practical use as an insecticide internationally. The effects of caffeine on insects remain largely unclear, and further research is needed." The study was published in Applied Entomology and Zoology.

Caffeine is well known for its ability to activate dopamine and elevate human mood. It is known to increase activity and affect sleep in flies, improve learning and memory and prolong the lifespan in bees. However, its effectiveness as an insecticide or for pest control has remained controversial, as experimental results have varied despite long-term testing.

The research group first conducted a preliminary experiment by giving flies sugar water with varying concentrations. They found that providing a 4% concentration of sugar water prolonged the lifespan of the fruit fly. Subsequently, the researchers conducted an experiment in which adult flies consumed 4% sugar water containing varying concentrations of caffeine. The results showed that sugar water with caffeine at concentrations of 0.5% or higher had a strong insecticidal effect, killing all the flies within a week. Meanwhile, lower concentrations of caffeine in sugar water had no insecticidal effect. The research group also found that caffeine decreased the locomotor activity and lipid content in adults.

The mechanisms underlying the associations between locomotor activity, lipid content and the shortened lifespan remain unclear. Nevertheless, the clear insecticidal effect of excessive caffeine consumption on flies demonstrated in this study is expected to contribute to the development of a caffeine-based insecticide.

Journal Information
Publication: Applied Entomology and Zoology
Title: Effects of caffeine on the longevity and locomotion activity of the common green bottle fly, Lucilia sericata (Diptera: Calliphoridae)
DOI: 10.1007/s13355-025-00893-0