[A strange sight] I want to know more! The mythical six-horned rhinoceros beetle, Diperix gerion! ~Part 1~

First of all, could you tell us about the characteristics of Dipelix geryon, which is featured in this special issue? (Hereafter referred to as Geryon)

The Gerion is a rhinoceros beetle said to live on the island of Java, characterized by its striking horns. It has a single sharp, edged horn on its head, and a flamboyant array of horns on its thorax that are so intricately arranged that it's impossible to count them all, almost like Godzilla's dorsal fin. There is no other rhinoceros beetle with such a complex and bold horn shape.

This species belongs to the Dipelicus genus, and its Japanese name comes from the fact that the type species, Dipelicus cantori, has five horns, or gokaku (pentagonal), as its name suggests. However, although Geryon belongs to the Dipelicus genus, it actually has six horns... so I think it's fair to call it Rokakumarukabuto. I think its scientific name comes from Geryon, a three-headed, six-legged monster that appeared in ancient Greek mythology.

Until now, it was a mysterious rhinoceros beetle that could only be seen in natural history paintings, right?

Aside from the specimen I obtained this time, the only other specimen remaining is a single lectotype specimen kept at the Humboldt Museum in Berlin, Germany. In a paper written in 1969 by Hungarian beetle researcher Sebö Endrödi, there is a very simple line drawing of a Gerion, and the specimen that served as the motif for this drawing was the specimen at the Humboldt Museum. This specimen is only recorded as being in the collection, and no photographs of it have ever been made public.

Another thing is that the illustrations in the magnum opus "Illustrations of Natural History" by Dru Drury, a British naturalist active in the early days of insect taxonomy in the 1700s, appear to suggest that at least one specimen that was used as a reference for drawing those illustrations must have still existed. However, most of the insect specimen collection that Drury built up has been scattered or lost.

Currently, only a few specimens from 200 to 300 years ago have miraculously survived, preserved in a few facilities such as the British Museum of Natural History. I have diligently researched past papers and asked famous collectors both in Japan and abroad about Gerion, but as expected, the only specimens reported in history are the one at the Humboldt Museum and the individual in Drury's illustration.

So until now, Geryon was a creature whose appearance had only been known through illustrations. Now that its true form has been revealed for the first time in beautiful photographs, I think beetle researchers around the world are amazed. They're probably wondering what this Japanese magazine is all about! (laughs).

It's quite unusual that such an impressive insect has barely appeared in the public eye until now.

That's right. There is a tendency that "the rarer the item, the less cool it is" (laughs). Even if a species is very rare at first, if it has a shape or color that appeals to collectors, demand in the market will increase, and in response, many specimen dealers, local collectors, and other people who make a business out of specimens will be eager to collect and sell them. As a result, the cooler the insect, the more it will end up circulating in the market.

As a result, species that don't attract much interest from people are often traded as rare species. The king of insects, the Hercules beetle (Dynastes hercules), is an extremely rare species that is originally found only in limited areas deep in the mountains of Guadeloupe and Dominica. However, these days, both wild and live specimens are circulating in abundance on the market. This is because people's demand has changed the difficulty of obtaining these insects.

So why has Geryon remained a mythical creature until now? There are many Javanese insects found in Japan, and it seems like such a fascinating insect should be better known.

The exact reason is unknown, so this is just speculation, but it is possible that their habitat was extremely localized, or that they became extinct due to deforestation.

The genus Stag Beetle, to which Gerion belongs, is generally not a particularly rare insect. In fact, specimens are widely distributed, and they are known for their habit of flying into lights, and the largest species, the Canthargo Stag Beetle, even comes to Japan as a live specimen. Gerion itself is unmistakably a Stag Beetle based on its morphological characteristics, so it is unlikely that its ecology would be significantly different from other species.

Furthermore, although it is unclear how reliable this is, the label and literature state that the beetle's habitat is Java. Java is home to many large and highly sought-after rhinoceros and stag beetles, including the Caucasus beetle (Chalcosoma chiron), and there are many local beetles collectors who make a living by collecting them and selling them to Japanese dealers.

It is hard to imagine that these insect-catching specialists would miss such a conspicuous rhinoceros beetle. Java itself is not an especially large island, so I think it may be that it has already become extinct, or that it is only found in a very localized forest somewhere.