The Sussex bat Group's newsletter, The Belfry, includes a warning about a danger to bats fed on mealworms. Apparently the adult beetles produce harmful hydroquinones which can contaminate the food which the larvae eat and which can be passed on to bats fed on them.
The message is that containers of mealworms should have adults removed as soon as they metamorphose.
This information comes from the following web site www.basicallybats.org/onlinebook/CHAPTER9.htm
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