Asked June 12, 2017, 1:52 PM EDT

Over the last several days, I've noticed these black hard shelled elongated beetles in my hay mound. They are solid black and have wings although I have not seen them fly. They are approx. 1/2" long. They are feeding on the chaff because I don't see them in the hay that is on higher tiers in the mound... just on the floor area. Are these insects harmful to my horses and if so, is there any way I can get rid of them without destroying my hay? Please and thanks for your time. We are in the process of putting our newly cut hay in the barn with this older hay (approx. 50 small square bales) today. Should I not store the new hay with last years hay that I'm having the beetle issue with. I've submitted a photo but it's not the best. Please call me if you have other questions or would like me to get more pics. Thank you. Cathy in Laingsburg

Shiawassee County Michigan

1 Response

Dear Cathy - I sent your image to our MSU entomologist expert and he responded with the following:

Those aren't blister beetles for sure. Blister beetles have "necks", that is, the pronotum is narrower than the head. They look like click beetles (Elateridae) or yellow mealworm adults, Tenebrio sp. (Tenebrionidae). You can send me some if you like.

To preserve and protect fragile specimens, it’s always best to submit insects in a small leak proof vial filled with rubbing alcohol or vinegar. Place the vial in a small zip-lock baggie, then in a small box or mailing tube and mail to

Diagnostic Services
578 Wilson Rd.
East Lansing MI 48824-6469

Be sure to include a note with your contact information including your email address.

You can download one of our submittal forms here:

Regards, Howard

I had wanted to make sure they weren't blister beetles, as blister beetles are extremely toxic to horses. However, I would suggest cleaning out your hay loft prior to storing your new hay.

I don't have your e-mail but you can contact me directly via e-mail: for follow-up. I will need your e-mail and/or phone number.


Chris Skelly