Prosopocoilus biplagiatus – Hong Kong’s hidden gem

And yet another post on another stag beetle species, seems I am on a roll these days 🙂
Prosopocoilus biplagiatus is a smallish stag beetle species, which looks similar to Prosopocoilus inquinatus and some other small Prosopocoilus species from Asia. That said it is a fascinating species for me mainly for two reasons:

Prospocoilus biplagiatus from Hong Kong, Big male

1. It is one of the very few stag beetles species that can be found in a big city, namely Hong Kong. The first time I became aware of them was when my friend O’cules Cheng showed them to me in 2003, and we tried to actually find them. This was an interesting and long nightwalk in the New Territorries, which sadly did not yield any beetles. We also checked for them on some bridges over the road that went to mainland China, but again, did not find anything. At that point in time he had also mentioned that, while not being rare, it seems that Prosopocoilus biplagiatus had evolved to not be attracted to light sources anymore, which is a useful insect ‘skill’ to have, given the amount of lights in a city like Hong Kong.
2. It seems (I have seen pictures on Instagram, thanks to Art Tomango for forwarding the pictures) that there is an option of rearing telodont specimen. This is very unusual, because all you ever seem to find in the wild are short mandible types. Supposedly, the trick was some secret self-made mat, but in my opinion, the key is low temperatures (16 degree Celsius). Something to aim for, as they look quite beautiful with long mandibles.

Prospocoilus biplagiatus from Hong Kong, F2 Trio

I got my larvae last year in November, from my good friend Daniel Ambühl. These were animals of Hong Kong origin, I believe an F1 from wild collected ones, and the dead imagines were bigger than any I had ever seen of that species from Hong Kong. Picture a 22-litre box with many larvae in it. There were around 40 in total. I placed these into separate containers, 500ml, filled with white rotten wood, mainly because many larvae were already past L2, and that was what they had been eating before. I figured I might end up with slightly smaller imagines than with kinshi or flake soil, but rather prefer to get all larvae to imagines. The common rule of thumb with beetle breeding is to let them experience as little change of conditions as possible. Even if the setup is not perfect, its better to wait for the next generation, than to stress them and risk death and even smaller imagines by introducing major changes. Think of them as tiny very old people – change is rarely good.

Prospocoilus biplagiatus from Hong Kong, F2 Male in artificial cocoon

The larvae started pupating from March onwards, while a few are still larvae, the majority has by now become beetles.

Prosopocoilus biplagiatus is a rather shy species that stays mostly inside the substrate and is only active at night, and none of the big feeders. It is so rare to see them at the jelly that I am actually asking myself whether they even feed as imagines. Also, they seem to be one of the more communal species, that can be kept together as larvae, provided there is enough space and food. I think those 40 larvae could have been kept together in a 20-litre box, without losing many.

Prospocoilus biplagiatus from Hong Kong, F2 pair

So far, I have only set up one breeding box for a trio in May. Similar setup to other stags: Compressed white-rot sawdust at the bottom of the container, well-watered and de-barked white rotten wood pieces, all topped off with loose white-rotten sawdust. Now I needed to check the box yesterday as I noticed some rain worms in the substrate. Not sure how they got in, but in my experience these are one of the worst pests to show up in Lucanidae and beetle breeding in general. Larvae tend to stagnate in growth, and females stop laying eggs. So, time to check. I found a disappointing 14 larvae, which were now separated into 500ml containers again. As a food source I filled the containers with flake soil, to aim for bigger beetles this time. The parent trio is still alive, so I set them up in a fresh container. One important piece of advice. This species prefers larger pieces of wood to lay eggs. In my setups they ignored smaller logs, and always seem to concentrate on the biggest log. Also, they like somewhat softer wood for laying eggs, but larvae can also be reared on relatively hard white rot wood. That summarizes my experience with Prosopocoilus biplagiatus from Hong Kong, an overall easy-going and good beginner species, with the challenge to the pros to rear a telodont giant 🙂

Prospocoilus biplagiatus from Hong Kong, F2 Male