A bin of warm, fermenting sawdust may not look like the foundation of a captive breeding program, but at the Butterfly House, it is a vital piece of the process.
The Butterfly House has a robust captive breeding program inside its Entomology Lab, creating new generations of animals to share with visitors. One hugely successful breeding program has been that of the jewel stag beetle (Lamprima adolphinae), sometimes called green stag beetle.
Over the past year, the Butterfly House has welcomed seven new jewel stag beetles through the program (as of May 2026). Behind each beetle is a months-long process of recreating a rainforest floor in miniature, complete with carefully fermented sawdust, the right conditions for larvae to grow, and months of patience.
By breeding generations of several beetle species in captivity, Butterfly House entomologists are helping reduce pressure on wild populations, educating visitors about one of nature’s most important decomposers, and sharing knowledge for future conservation efforts.
Below, Tad Yankoski, Senior Entomologist at the Butterfly House, explains how they are creating the ideal environment to grow future generations of jewel stag beetles.
Colorful Ambassadors
With metallic colors that can shimmer in shades of green, gold, and copper, jewel stag beetles may be small, but they are hard to overlook. Native to the West Papua region of Indonesia, these beetles are known for their brilliant coloration and relatively short development from larva to adult.
At the Butterfly House, Jewel Stag Beetles make ideal ambassador animals, helping visitors better appreciate the beauty and ecological importance of insects.
Why breed Beetles?
“So much of what we talk about is the importance of these animals in their natural habitat,” Yankoski says. “They play an important role in the nutrient cycle of their environments as decomposers who break down wood into soil. So it is then a little hypocritical if we are taking those animals out of the environment.”
Captive breeding of beetles provides a sustainable supply of animals for public education. By breeding several generations of beetles in captivity, the Butterfly House reduces the number of beetles being taken out of their natural habitat.
“It is important to do everything we can as zoos and insectariums to be self-sufficient,” Yankoski said.
Another benefit of captive breeding is the protection and continuation of at-risk species. The jewel stag beetle is not technically considered endangered as of 2026, but Yankoski says all that could shift quickly.
“I would argue that all rainforest habitats right now are to some extent threatened because of logging, agriculture, urban creep, and climate change,” Yankoski says. “All these things are putting pressure on the rainforest habitat and the insects that live there.”
If a greater conservation need arises, entomologists now know how to quickly rebuild beetle populations for several species.
Building A Jewel Stag beetle population
Before a sustainable beetle population can grow, the Butterfly House first has to start with adult beetles.
About once a year, the Butterfly House receives a large shipment of several beetle species from Kingdom of Beetles Taiwan, a breeder in Thailand. These beetles are not taken from their natural habitats, but come from several generations of bred beetles.
Even after the Butterfly House has successfully bred a few generations of beetles, these new adult beetles are important for genetic diversity in the growing population.
Once adults arrive, the next challenge begins: successfully creating the conditions for a new generation.
The Jewel Stag Beetle Life Cycles
Eggs
Like many insects, jewel stag beetles begin their life cycle as eggs. These eggs have already been fertilized through the mating process and are laid by the adult female beetle. If substrate conditions aren’t just right, the female will not lay a single egg.
Larva
Larvae then emerge from these eggs. Entomologists actually consider the larval stage to be three substages based on the number of times a larva has molted. Jewel stag beetles molt three times, eventually growing to about 1.5 inches long.
Pupa
Next comes the pupa stage, which can last several months for jewel stag beetles. Though sometimes called a dormant stage, it is during this time that larvae undergo a major metamorphosis, breaking down their tissue and remodeling their bodies to develop wings, legs, and, in males, large mandibles.
Once fully formed, the beetles will wait for the ideal setting to emerge from their puparium.
“Depending on the species, they might wait underground for weeks or longer before they come up,” says Yankoski. “Those with shorter adult lifespans tend to come up earlier for food and mating. But it is not unheard of for adults to be in their puparium for a month or more.”
Beetle
Once they emerge from their puparium, jewel stag beetles usually live around six months — a short lifespan compared to other beetles like the elephant beetle (Megasoma elephas), which can live up to three years in the larval stage alone.
Yankoski says the short lifespan of jewel stag beetles is not necessarily a bad thing when it comes to captive breeding.
“One of the nice things about these jewel stag beetles is that the generation time is significantly shorter, so that if we really figure out what we’re doing, we can grow a big population and have a lot to show in a relatively short amount of time.”
Beetles have figured out the natural cycle of breeding and creating new generations. The challenge comes when entomologists try to recreate this process in a captive environment.
“It’s all about creating the perfect natural environment for them in a little box,” Yankoski said. “That’s the tricky thing, of replicating what they would have in forests.”
Recreating that process outside a rainforest, however, is easier said than done.
Sawdust: The Secret Ingredient
If beetles had a love language, it would be food. Yankoski says the most important part of beetle breeding is creating food for the adults to lay eggs in and for the larvae to feed on.
“The larvae are very picky about what they’ll eat,” says Yankoski. “Most of the ones we’re working with eat some form of rotting wood. They need rotting logs or a sawdust-rich substrate.”
Unfortunately, finding rotting logs for beetle breeding isn’t an easy task in the U.S., which is why the Butterfly House team has developed its own method for creating the food these beetles need.
The process involves buying oak sawdust pellets – often used for smoking meats – rehydrating these pellets, and fostering an environment for fermentation and fungus to thrive. This process accelerates the natural decomposition process of the wood, mirroring in weeks what fungi would do to fallen trees over the course of years on the rainforest floor.
“It goes through this whole biological process where it heats up, and it’s sort of cooking itself,” explains Yankoski. “At the end of it, you have a sawdust that is more in line with what you’d see in the woods on a log that’s been lying on the forest floor for a couple of years.”
Standing on Each Other’s Shoulders
Yankoski notes that beetle breeders and entomologists in Southeast Asia figured out the importance of food for larvae a long time ago. But because of supply limits in North America, entomologists have had to get creative with the sawdust substrate.
Yankoski shared some of these methods in a 2016 paper with colleagues through the Association of Zoos and Aquariums’ Terrestrial Invertebrate Taxon Advisory Group at the annual Invertebrates in Education and Conservation Conference. Since then, other zoos, insectariums, and universities have tried and adapted the method.
“Other institutions have expanded on it dramatically,” says Yankoski. “So we all sort of stand on each other’s shoulders.”
If the breeding program continues to succeed, future generations of jewel stag beetles raised at the Butterfly House may eventually be shared with other institutions — expanding opportunities for education while reducing pressure on wild populations.
Jessika Eidson | Public Information Officer
Thanks to Tad Yankoski and Chris Hartley for their contributing expertise.
Leave a Reply