Yesterday, my dad told me:

“I saw a lot of flies as I was moving the potted plants and compost bins. They flew in swarms. I took an insecticide and sprayed them.”

I know you are probably curious – if not, shocked – about the flies. Like you, we hate to associate flies with composting, especially for apartment composting.

But first, I’d like to voice my slight annoyance about the need to shift all my apartment’s outdoor potted plants and compost bins up against our doorstep.

Apparently, there’s some construction work going on at our block over the next few days, and we were informed to make space for the workers. Now, entering or leaving my HDB’s apartment is like walking through an unexpected forest. (Sigh.)

Alright, now back to the flies.

Usually, I would quietly (internally) go berserk upon hearing about creepy crawlies. Mind you, I scream/squeal at dead cockroaches.

But over the past few days, Joe and I had the honour and pleasure of having a fellow composter chance upon this site and sharing his experiences with us through email.

He managed to identify the maggot-looking things in our compost bins as the larvae of the Black Soldier Fly.

Here are some points he shared in his email:

  • Black Soldier Fly larvae look like maggots, off-white in colour with a segmented body (each segment looks like a ring)
  • BSFs are beneficial insects – they are very good for food waste recycling
  • They do not disturb humans
  • If the flies in our compost bins are indeed BSF, we will see many more – the adult fly can lay about 900 eggs

Joe met him this afternoon too, and came back with more information about BSFs:

  • They appear to be tame – they don’t immediately fly away, even in close proximity with humans
  • They are only interested in rotting/rotten food
  • Unlike normal houseflies, BSFs tend not to enter households

Larvae of Black Solider Fly. Image from

Adult Black Soldier Fly. Image from

I still remember the day when we tried to identify the larvae with the help of my dad. He said that the larvae produce organisms that help to compost organic wastes, and that they are not harmful or poisonous to humans. However, he only went to as far as (mistakenly) identifying them as beetle larvae.

Well, at least my dad got it half right πŸ™‚

So, I thought about how everything came together: My dad only noticed the flies when he moved the potted plants and compost bins. We also didn’t see the BSFs at all over the past few weeks, even though they were there all the time!

After having an insight about BSFs, I wish my dad didn’t wield a can of insecticide to get rid of them. For sure, we ain’t gonna do anything rash like that again. Right, daddy?

Nevertheless, we believe thereΒ must be several remaining and residing inside the compost bins!

To find out more about BSFs, you can refer to plenty of online resources. Joe might be doing some secondary research on BSFs too, so do check back often for more updates!


8 responses »

  1. Amanda says:

    Nice post! I just found your post after writing mine. Great minds think alike πŸ™‚

  2. jessica says:

    thanks so much!!!! i was inspired by your blog to make my own compost bins, and I just noticed those maggots and was really worried about it! But then when I saw the pictures I knew that we also have black soldier flies, because we’ve seen them flying around the patio!! Thanks so much for your inspiration and also for easing my worried mind!!!

    • Hi Jessica!

      Wow, we are almost envious to know you’ve got black soldier flies in your pile! Given the chance, we’d love to breed them cos we know they are great in several ways (i.e. composting, feeding to fish etc)

      Do keep us in the loop about your composting progress! We’re always excited to hear from fellow composters πŸ˜€

  3. jessica says:

    well, about 4 weeks into our compost and things are going great. the larvae keep the garbage really down to a minimum. in only four weeks, the garbage continues to stay only half full! they break it down so quickly.

    The only problem is that we didn’t anticipate the quickness with which they’d mulitply and try to escape to freedom to become flies. We’ve had them crawling all over the place all the time. I’m not afraid of them, I think they’re quite funny, but my mother in law shrieked in terror when she saw them, so they’re not very nice if you have house guests.

    Luckily, they can’t climb vertically, so we just sweep them up and put them all in one spot, in a container in a shady spot to let birds come and eat them. That sounds horrible!!! Luckily we have a large roof the birds aren’t scared to come find their new food on. Apparently it would be great if we had chickens, because we could feed the worms to them, but we don’t have enough space for them! So, really to have black soldier fly larvae, you really need a good system or it can become terrible pretty quickly. The containers online that they sell are great, but what can you do with the worms after that if you don’t have livestock or animals to feed them to? We don’t want a plague of worms!!

    • Sarah says:

      Our apologies for this extremely belated reply, we’ve recently read your comment again and can’t help but to still feel envious about how you are getting BSFs so easily! πŸ˜‰ One good way is to feed them to fish with mouths big enough to eat them fat, juicy larvae (i.e. koi, adult tilapias etc). Birds are the easiest too, since they exist everywhere in abundance. We’re sorry to hear that BSFs can be a nuisance – a proper system is indeed needed to keep them managed and growing well even for a side business/profit!

  4. w3 says:

    Hi. Im new. I started composting last week. I found maggots, fat maggots in my compost. What should i do? I get confused at all the reading. Please guide me. Thank you!

    • Sarah says:

      Hi w3,

      Thank you for getting in touch. We’re sorry for missing your comment till now. Are the maggots still residing in your bin? If they are in the bin and not outside, you can safely ignore them as long as they are not behaving like pests. It’s a normal part of the composting process, and maggots are common if your bin has been placed outdoors.

      Another way to prevent maggots from occurring would be to ensure that the top of your bin is dry (i.e. adding a lot of shredded newspapers, or a layer of cardboard, hay etc). We have also tried adding homemade garlic and chilli spray, or lemongrass into our bin. These help reduce pests if they are starting to be a problem.

      Hope this helps, do feel free to ask us questions again in any of our social media links:

      Facebook –
      Twitter –
      Instagram –

      Cheers πŸ™‚

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s