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Forked Fungus Beetle

Male forked fungus beetle
Male forked fungus beetle, Bolitotherus cornutus (Coleoptera: Tenebrionidae)

Dr. Arthur V. Evans teams up with WCVE Public Radio producer Steve Clark for a weekly feature, “What’s Bugging You?,” which airs during NPR’s Morning Edition. The program takes its name from another of Evans’ books “What’s Bugging You – A Fond Look at the Animals We Love to Hate.”

SC: I'm Steve Clark with Dr. Art Evans, entomologist, and this is What’s Bugging You. Today Art is presenting for the first time, the forked fungus beetle.

AE: It's easy for you to say.

SC: Forked fungus beetle.

AE: All right, all right show off. (laughing) I've always been fascinated with these beetles. You'll find them on shelf fungi out in the woods, and the males are very distinctive because they have a pair of very distinctive horns on their midsection, their prothorax, or not. Some of them have well-developed horns, some of them have just little nubbins, some of them hardly anything at all. And they feed on the fruiting bodies of the fungus usually at night, but occasionally you'll find them either hiding under bark near fungus during the day or maybe just kind of wandering around. But I've always been fascinated with them because the males use those horns to dislodge other males that are copulating with females.

SC: In the process, right?

AE: Right and you would think that the horn size would influence the outcome, that the beetles with the bigger horns would do better.

SC: Well, don't they?

AE: They don't. It turns out that horn size probably is helpful, but what's more helpful is just being a bigger beetle overall and having a good grip. If you can hang on to the female and prevent another male from dislodging you, you're more likely to complete the act and pass your genes along to the next generation. Another little tidbit that I've discovered over the years, there was some research done that shows that horn size in males is determined by the mother. If she selects a good beefy fungus upon which to lay her eggs, her sons will have plenty of food to eat as larvae and that will ensure that they have well-developed horns. If she doesn't choose well or something happens to that particular fungus, then of course the males that complete their development will have less than fully developed horns.

SC: Now, the appearance of this beetle is that it looks like a fungus itself.

AE: Well, they're very cryptic. They're heavily sculptured. They're dull gray - look like a little dirt clod sitting on top of the, the fungus. I've been in several places over the years where I'll find a shelf fungus, and I'll look around, and I'll see them walking over the fungus at night or underneath. Sometimes that's where I find them during the day. Occasionally I've seen them at lights. They are attracted to lights. They have an incredibly hard body. They resemble a type of a scarab beetle, if you will, called the hide beetles, which you'll find on carcasses and bird nests too. They have that same compact shape, very rough, dull-looking appearance. They'll tuck in their legs pretending to be dead, and if they continue to feel threatened they’ll release a toxic chemical that has a very pungent odor and apparently a very bitter taste.

SC: What is a shelf fungus?

AE: Oh, if you look at the trunk of a tree and you'll see these fungi that are sort of growing shelf-like. They're very hard.

SC: Ah, yes.

AE: And sometimes you'll see just one, sometimes there will be groups of them. There are all kinds of beetles and other insects that are associated with these fungi. Occasionally I've broken off a shelf fungus and you'll see this creamy yellow larva or grub right at the base of the fungus where it attaches to the tree, and that's the larva of this fork fungus beetle.

SC: Dr. Art Evans is a Research Associate at the Virginia Museum of Natural History. You’ll find photos, audio, and links to the museum and Art’s Facebook page at

Tune-in each Tuesday at 8:45 a.m. or at 5:44 p.m. on 88.9 WCVE, Richmond’s Public Radio station.


On this weeks episode, Entomologist Dr. Art Evans and WCVE producer Steve Clark discuss the natural history of the forked fungus beetle.


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