Hello all,
We performed an inspection this morning of a nuc we have. To our surprise we found about 20 “larvae” wriggling on the bottom board, approximately 15-20mm in length.
All the 5 frames appeared to be healthy with an abundance of bees.
We killed all of the larvae we found and changed the bottom board and plan to repeat at the weekend.
Can anyone identify what they are and should we be concerned?
Yuck. Looks like wax moth larvae to me - more than I’d be comfortable with to leave to the bees to control. I’d recommend taking a thorough look at all the corners, crevices and grooves on frame joints, inner cover, brood box and bottom board - especially the bottom board. If you have a Flow issued bottom board or similar, there is more than one position for the coreflute to be placed - meaning there’s a vacant set of wax moth condos under there 
You can also hang a wax moth trap somewhere near/behind your hive -
Could they be soldier fly larvae? If so, send them to @JeffH for his compost heap. They look a little dark for wax moth. 
If they are soldier fly larvae, are they a problem? We live in a rainforest/heavily canopied property so organic matter is everywhere.
I don’t think they are a problem for bees at all. If anything, they may munch a few wax moth and SHB larvae, but @JeffH knows more about them than I do. 
Hi Felmo, as @Dawn_SD suggests, Black Soldier Fly larvae, without a doubt. No need to kill them. Just throw them in the garden. Black soldier flies are good flies, different to house or blow flies. The adults don’t search for food, only somewhere to lay eggs after mating.
How they got on the bottom board, would be a mystery 
Would you believe that they breed them in huge numbers for the purpose of producing bio-fuel from the bodies of the larvae, like in your photo.
Thank you @JeffH. I don’t know how that answer came into my brain, but when I saw those fat, dark larvae, I immediately thought of your compost heaps. 
By the way @JeffH, my English grammar teacher preferred “different from” and would deduct marks from anyone who wrote “different to”… 
The internet thinks it is more complicated than that, but I am just passing on what was taught in a British all-girls school. 
Thank you Dawn Your English grammar teacher was a hard task master. I would have failed English for sure.
Thanks for thinking of my compost bin. cheers
PS, I learned about prepositions while listening to an old comedy radio program “Yes, What”. I still don’t understand them.
@Dawn_SD I edited my post. I meant to say “prepositions”. It’s amazing the difference a one letter typo makes to the whole context of a sentence.
We changed the bottom board of the nuc today.
No sign of any soldier fly larvae but a little of chalkbrood. Maybe that is what they were feeding on.
Thanks for all your replies. It is a bit daunting to be confronted with numerous larvae wiggling around when you initially encounter them. Reminds me of leeches moving on mass.
Hi Felmo, I’ve never seen BSFL in a hive or on the bottom board, however I’ve encountered them feeding on slumgum en masse. I used to wonder how they got under the lid of buckets, in order to lay their eggs in the slumgum. Consequently, they lay their eggs outside the lid, then the eggs hatch before the tiny grubs crawl under the slightly loose fitting lid, then onto the food, where they develop into grubs like the ones in your photo.
