Parasitic bugs found in a crabitat

A member at HCA discovered these images/bug.jpg”>bugs images/bug2.jpg”>bugs in her tank and inside the shells of her dead crabs.
This is the info collected at HCA in regards to these bugs:

Post subject: Jinjurale’s bug identified!

Hi Guys,

This is Megaselia scalaris (Loew), a cosmopolitan, often synanthropic,
polyphagous, scavenging phorid. They often attack injured or weakened
invertebrates, especially in cultures of cockroaches, crickets,
tarantulas, etc., but I’ve never heard of them infesting hermit crabs
until now. Henry Disney (who keeps track of such things) will also be
interested, so I cc’d him on this too.


Brian V. Brown
Curator, Entomology Section
Natural History Museum of Los Angeles County
900 Exposition Boulevard
Los Angeles, CA, 90007, USA
Telephone 213 763-3363
FAX 213 746-2999

Wow. When he says polyphageous (eats anything), he means it. These flies have been found living in shoe polish, blue paint, human cadavers in formaldehyde and lungs in living people ! It also may be responsible for an outbreak of rashes in US schools. They are a “neo-tropical” species, but also a “tramp” species, meaning they hitch rides all over the world in shipments. It probably was in the crab when purchased, since it was at the store and are rare in cold climes like Minnesota. This is something that could happen again, so we should know it is out there.

They appear when organic matter is rotting, exactly what Melin said. I guess that’s why she’s the teacher. Henry Disney was cc’ed this message. He is THE world expert on phorids, so you guys are famous now and will probably end up in some text book.

And let’s not talk about folk-cures.


I have these bugs in my classroom right now. They are always a clear sign something is amiss. Yep, they come with the crickets (As do the mites) and they feed on the dead. I am not concerned about them at all. I never see them unless there is decaying matter. Once the body is discovered they take off… presumably for another host. I have them because i was hoping my crab might be molting, but he died. I knew he died by the flies and later the smell. Bugs really are good! The are a strong indication of lots of things. I think.

One thing i do recommend is cleaning the tank or area where you might have found the bug. They come to dead creatures fast. And my doors and windows are always open. I think that is part of why they come so fast (not to mention climate) BUT, if they are laying eggs in the substrate then you want to be sure those are gone. I have never seen them on a molter, but i dont want to take the chance.

Good show Tardigrade!! Did it say they drown in water? Cuz i am pretty sure they do!

Thanks for the props above. Honestly, i am only speaking from experience not scientific knowledge. I observe everthing though. Sometimes a little too much…


Very valuable information! So will there be a follow up on how to deal with this with the hermit crabs?

What happens when you have the bugs in your tank but no decaying matter for them? Will they eat on the crabs?? Are they drowndable???


Daethian, i have been looking stuff up on line, with Tardigrade’s help, and it seems to be the same thing i have had.

When there is no decaying matter, the flies leave. I would certainly bathe the crabs on a regular basis. And i will do that too. Just in case larva has been deposited. But I haven’t seen them in my main tank. Just my ISO where my crab died.

Every time i have had a death, they showed up. And left almost as quickly.

Honestly and i don’t mean to say the person with infestation is wrong, but i don’t think the bugs stay unless there is some decay or bacteria festering. In her original post she said she could hardly stand it the stink was so bad and that she might have a dead crab.

My guess is that the flies noticed the death early on. As soon as that crab passed… If they are bad enough they could be deposiing eggs. Only my guess on what i have seen with mine and read… Bathing and a complete clean up should take care of the problem.

JUST my best guess… Still looking into it and I know others have entomologists or some contacts working on this.


Thank you! That’s interesting and I’m glad we found out for sure what it is. I collect bugs that appear in crabitats, so here’s another one for my collection
I still wonder about the crippled wings – maybe the fly was newly hatched and the wings had not hardened yet?
I found an article that states that they are attracted to those yellow sticky traps. I used those in my crabitat a while ago to get rid of gnats and they can be attachted to the lid of the crabitat where the crabs cannot reach it.


Thanks Melin.

Obviously the drastic measures given before are not necessary then. Clean and sterilize everything to remove any eggs or larvae and it should be fine.

Great job guys!!!

Sidenote: I believe someone said these are typical in warmer areas.


  1. Okay…I just gave Joey a bath… and when I came home I saw him with his poo all over his claw and he two legs by his claw…I think he has been eating his poopie. I tried to give him another bath but it did’nt come off! it that bad for them?

  2. There are only two people that I know of that have seen the bugs. They only eat decaying matter so as long as your crab is alive they won’t even be around. If you live somewhere that is warm year round like say Florida you may have to keep an eye out. Otherwise don’t worry.

    Your fruit treat sounds good. I feed all organic foods and there is a lady who creates recipes for crabbies. She is on the crabstreetjournal website. I buy coconut shredded in a bag instead of trying to buy whole coconuts. Another thing my crabs really like is hotdogs and sardines. The sardines are very stinky but they love them. I have a list of acceptable foods under What can my crab eat?

    Don’t wait until Nemo is actually shedding his exo to move him! Him may decide to dig down in the main tank and you won’t be able to move him. I have a article here on molting signs, its called Molting or Dying. Read that so you will know what to look for BEFORE its already happening.

    Don’t worry about the poop. Crabs actually eat poop and its okay. In the wild they are scavengers and eat all sorts of garbage and rotting stuff. Apparently turtle poop is really good for them.

  3. Okay first of all….You said cookies remmember my name… well I try to regester for something…it says i need to enable cookies. I dont have them. How did it remmember my name that one time when I dont even have it?

  4. I think I already read the molting or dying thing when I thought Joey was dead. Oh and its too late for Nemo. He has already dug so deep. He dug under the log and I could see him popping out on the other side. I don’t think he is molting though. My friend said that he molted 4 weeks before that and I just remmembered it… Thats why hhis shell is so big on him. I even went to her house and saw the little molting crabbie… I have no idea why I forgot.

    And>…EEWWWWWW they eat the poopie. gross. And you can feed you crabbles HOT DOGS? I don’t know if that will be good but I will definatly try the stinky sardenes. The coconut I but is shredded so I can mash it comes in a big bag with the name _” Euguea’s islands” on it as a logo. is that what you have?

    ANd do you tell your crabs apart? I know they have different shells. but since you have so many, its probably MOLT-&-SWITCH mania! How do you tell them all apart?

  5. I already know about the cab street journal, I am a member. I AM always online because I leave mmy computer on…you will see SABBY by the bottom.

    Also I was obsserving my hermit crabs and I found something that just ,made me laugh. Well Nemo andJoey are still fighting, And I just noticet how territorial Joey is. But when they started to walk around in circles facing eachother, They raize ther legs to make them selves look scarier or to show they want to fight…I also noticed thet Nemo is small…so he climbs his shell on the glass wall of the tank , you know where his shell is leaning on the glass, WAAAAAAAAAAAY up high to make him look bigger.. Then JOey did that, And nemo ran like a chicken. – They are just fighting because both of the crabbies are very territorial. ~ but its funny with the LEGS UP HIGH!!!

Leave a Reply