Geoff McCabe

Rhinoceros Beetle Larvae

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rhinoceros beetle larva

Friendly Transparent Underground Monsters

We discovered these large, transparent grubs living in the earth near the roots of our bananas. They look thoroughly vile, and with their large sharp mandibles, they seem to be able to deliver a painful bite. They are about the length and thickness of a man’s thumb.

No one knew what they were, but our workers were convinced that they were destroying our banana plant roots (although the plants seem healthy enough) and they said they were killing these pests.

But were they really the enemies of our bananas? I took these photos and video to help identify what they were. A Google Image Search didn’t turn up anything useful. I tried searches such as “large transparent underground insects” but was only coming up with photos of cicadas and dragonflies with their transparent wings, plus the usual assortment of unrelated junk that Google Image Search delivers.

transparent underground insect / grubThen I remembered that many years ago, my friend Michael, a conservationist who used to live in Montezuma, had told me about the huge transparent grubs we might find underground, which were larva of some type of beetle. Quickly I was able to discover that they were… rhinoceros beetle larvae, a.k.a. “escarabajo rinoceronte” in spanish.

What do Rhinoceros Beetle Larvae Eat?

I was unable to determine, searching on the internet, whether they were eating our banana roots or not. Various sources describe them as eating “rotting wood and roots”. I’ve learned that in the Costa Rica jungles, one must not judge a book by its cover, and that everything has its place here. I suspect that these beetles are actually helping us. Bananas trees grow in groups, with each large stalk giving a single bunch of bananas, then dying, leaving roots underground that have spread out to form new plants. Perhaps these larvae are eating those dead roots, helping to process this material into soil, and creating space underground so that more bananas can grow. That would make them friends to the jungle

Rhinoceros Beetle Larvae Video

Hercules Beetle at Anamaya

This is what a hercules beetle larva grows into, although the larva in the photos I think grow into a smaller species than the one in the video. The hercules beetle is a type of rhinoceros beetle, which is a a type of scarab beetle also.

Further Reading

Hercules Beetles in Costa Rica – info on the rhinoceros/hercules beetles of Costa Rica
Dynastes Hercules – Read about the Hercules beetle species
Wikipedia Hercules Beetles