Rearing beetles from fungus
I have been asked by fellow bugguide contributors for advice on rearing beetles from fungus. It's pretty easy really for those collected in tree fungus or conks.
It's my impression that fungus feeders don't move in till the fungus is loaded with all the nutrition they'll need, so it doesn't matter that a fruiting body is severed from its mycellium. In fact, Dorcatominae don't arrive till the fungus is long dead.
The main precaution for rearing beetle larvae in fungus is to keep it well ventilated so mold doesn't grow all over it. Depending on fungus type, outgassing is also a danger to larvae that can be minimized with good ventilation. I have lost several batches of larvae to outgassing in a closed or small-mouthed container. Especially for softer fungi you will normally need a large-mouthed container like a tray, baking pan, or mixing bowl, covered with fine-mesh screen or netting to contain the beetles when they mature.
When I collect beetle larvae from mushrooms I now keep the larvae separate from their food supply just to avoid outgassing problems before I get them home. It's amazing how fast lethal levels can develop. I use clear polyethylene pill sorters to seperate live specimens I think might kill or injure each other (probably unnecessary for most small-mandibled fungus feeders) and a wad of plastic grocery bags for collecting foodstuff like bark, wood chunks, or fungi.
I presently have 20 or more forked fungus beetles in an open bowl of conk peices and they show no inclination to leave. I wouldn't try that with tiny dorcatomines though; they're not inclined to hang around. Expect loads of fungus gnats to issue from your fungus.
Shelf or bracket-like tree fungi, including large conks, should be kept fairly dry. Larvae that feed on them are adapted to endure long dry stretches. I spray them with a squirt bottle every few days, by which time they are usually quite dry.
Be sure to include a good photo or two of the fungus when you post larval and adult images as many beetles are host-specific and fungus type can help in their identification or even add to natural history data about the species.