Rhino beetles like body butter

An exceptional partnership between a high school student and an extension entomologist has resulted in scientific research that may be useful in curtailing the coconut rhinoceros beetle (CRB), Oryctes rhinoceros, that is plaguing Guam. The partnership began when Anran Li visited Aubrey Moore, extension entomologist at the University of Guam, looking for suggestions for a science project involving the CRB. Anran's first idea was to take dead rhino beetles and clear their skeletons with acids. Aubrey did not think the experiment would produce the outcome Anran imagined, but happily provided the dead beetles. Anran was not excited by his results, so he returned to speak with Moore. He told Aubrey that he was interested in insect behavior and how pheromones work. Moore mentioned that in a survey of the coconut rhinoceros beetle conducted on the grounds of the Pacific Islands Club he noticed that the beetles had heavily damaged a cluster of coconut trees around the outdoor spa. He wondered whether the products used in the spa attracted the beetles.

Anran developed his hypothesis; products used at the spa have fragrances that attract both male and female adult rhinoceros beetles. He headed to Jiivana Spa to obtain samples of some of the most common products they use on their clients. One of these products is a lotion called "Body Butter." To measure how attractive the various fragrances were to the beetles, he designed an olfactometer. The design was simple but effective. Aubrey admits, "His olfactometer worked better than one I made."

Anran's olfactometer consists of five Plexiglas boxes with holes drilled to allow the beetles to breath and to insert tubing for pathways. All of the boxes had to be extremely sturdy and escape-proof as the beetles are notoriously strong and single-minded. He positioned one box in the center with flexible tubing mounted on the top that connected to an exhaust fan. The other four boxes radiated out like satellites linked by tubing to the central box. To test his device, Anran put two proven attractants for the CRB, the pheromone used commercially to trap Oryctes rhinoceros and the pheromone used for Arabian rhinos, another species of beetle, in two of the four boxes. These pheromones were taped over breathing holes so that when the exhaust fan was running air would flow over the pheromones down the tubes and into the center box, which held the 10 beetles. All the beetles started in the center box, but eventually they began traveling down the tubes to satellite boxes. All but one of the beetles ended up in the box with the Oryctes rhinoceros pheromone lure.

Assured that the olfactometer was working, Anran proceeded to test his hypothesis.

He put the spa products in three of the satellite boxes and the pheromone lure used to trap Oryctes rhinoceros beetles as a control in the fourth box. After placing the 10 beetles in the center box, Anran conducted three separate trials. The results of the trials found 15 hits in the box with the lure, 7 hits with the Body Butter, and one hit each in the remaining boxes. These numbers are highly statistically significant and demonstrate that the Body Butter is at least half as attractive to the beetles as the commercially used lure.

Anran Li presented his research at the St. John's science fair and won first place, which entitles him to enter his project in the Kyoto Super Science Fair in October. "I was impressed by Anran's enthusiasm, his gung-ho attitude and his very methodical approach to the experiment," says Aubrey Moore. Anran Li believes that it was Aubrey's excellent guidance that helped him win first place. This may be the beginning of a long-term collaboration. They are both wondering what the key ingredient is in the Body Butter that attracts the beetles. Perhaps the next experiment will involve identifying the ingredients that make up the Body Butter and then testing each one with the olfactometer. The research possibilities are endless for an up-and-coming scientist and his mentor. It is possible that they may find a powerful attractant which might even be better than the commercially available pheromone lure currently used to trap rhino beetles.

Aubrey Moore is an entomologist and researcher at the University of Guam and he continues to play an important role in the CRB eradication campaign on Guam. Since September 2007, he has worked with federal and local agencies in educating the public and trapping rhinos in an attempt to eradicate the population of rhino beetles from Guam before they devour the coconut trees on the island. Anran Li has been interested in science since he was a child and is currently a sophomore at St. John's School. Both Aubrey and Anran recommend keeping your Body Butter away from your coconut trees!

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