Thanks for reaching out with this beekeeping question. 

MSU doesn't offer in-person colony necropsies ("necropsy" is an "autopsy" for animals), but we encourage beekeepers to inspect deadouts to try to determine the cause of the loss. Many winter losses in Michigan can be attributed to varroa mites and associated viruses or to starvation. Starvation is normally easy to determine because usually the beekeeper won't find any honey left in the hive next to the dead cluster of bees. Varroa and associated viruses are a really common cause of colony loss, even in colonies that were managed/treated for mites in the beekeeping season. You can learn more about loss from varroa through these resources:

Why Did My Honey Bees Die?

You can send questions specific to beekeeping and pollinators through the Ask Extension form at Questions? - Michigan Pollinator Initiative (msu.edu), which go directly to our apiculture/pollinator team.

Feel free to reach out with follow up question.

Happy beekeeping!