Falling in Love among the Mushrooms: The Horned Fungus Beetle
- HYUN SIM
- Nov 12
- 3 min read
The Horned Fungus Beetle (Bolitotherus Cornutus) is a species of darkling beetle that got its name from its distinct appearance and habitat. It is not the largest beetle; the adults grow only to around 10-12 mm in length. The width only reaches about 3.5-4.0 mm (AskIFAS). Its elytra and head are rough with numerous bumps dotting the surface. This trait was developed to aid in camouflage and defense. Its lifespan is around 8 years. Another distinct trait is its unique horns that have multiple uses.
The horns of the Horned Fungus Beetle have tiny hairs called setae on the underside of the end of the horn. Females lack these horns but are still influenced by them. Females have demonstrated a tendency to select males with larger horns for reproduction (Inaturalist). These horns are also used in fights against other males. They use these horns to contest for habitat and females. Females will tend to select males with a large section of shelf fungus since this is where all reproduction happens. Males will attempt to push or flip the opposing male off the fungal platform to establish dominance over the section or female. With these two things established, mating begins.
The Horned Fungus Beetle has a very long mating ritual lasting multiple hours. The first phase after establishing dominance over the fungal platform and the female starts when the male climbs on top of the female, facing the opposite way. This is the courtship phase. It stays in this position for 10 minutes to several hours and romantically strokes its partner's horn (Inaturalist). Once this phase is completed, the male will dismount and change position to begin reproducing. The female has the ability to completely cover up her anus using her anus sternite (AskIFAS). This is a plate located at the back of the abdomen close to the anus. If the female accepts, the female keeps its anus accessible and the mating begins. Once mating is completed, the male stays on the female for hours to guard her from other males.
The Horned Fungus Beetle lays fewer eggs than its Darkling beetle siblings. Each mating session only produces around one egg and only occurs around 10-12 times each mating season. The mating season is usually from June to August (AskIFAS).
The eggs hatch around 16 days after they are laid. The hatched larvae will burrow into the fungus platform upon hatching and feed on the interior. They spend the winter inside the fungus tissues and emerge as adults in the summer (AskIFAS). During the pupal stage, the larvae are susceptible to predators, including their siblings. There are many instances where a Horned Fungus larva will be consumed while in its pupal stage by other Horned Fungus larvae (Inaturalist).
The Horned Fungus Beetle is a target for many predators, such as rodents or wasps. It can also be consumed by the fungi that it resides in. There are many instances of the ycelium taking over the bodies of the larvae and using them for sustenance.
With all these predators, the Horned Fungus Beetle boasts many abilities to hide and fend off predators. On top of its durable exoskeleton, the colors and design of the elytra and head aid in camouflage. It is capable of warding off predators by secreting a chemical from its backside that is described to be foul-smelling, nauseating, and paiful to the oral glands of a lot of its predators (AskIFAS).
It's incredible that this insect can be seen living its life on little fungal platforms that can become arenas and places of courtship. The Horned Fungus Beetle boasts one of the longest and most intricate mating procedures in the insect world. It is found all over the world and in a unique habitat. The next time you see a cluster of fungi in a platform-style arrangement, take a close look, and you might see some romance.
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