Oh! Oh!...Black Soldier Flies in your Worm Bin?

Oh! Oh!...Black Soldier Flies in your Worm Bin?

Help for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request: 
Hi Master Gardeners, I live in Oakley and have had a worm bin in the backyard for several years. I recently noticed some other creatures in the worm bin that look like some kind of larvae, but they do move around. There are many of these in the bin, probably a hundred or so. I have enclosed two pictures of them, one in the worm bin and one in a glass jar. Are you able to tell me what they are and if they are harmful? There don't seem to be very many worms left in the bin, which used to have many worms. Thank you for your help.

Black Soldier Fly <br>in worm bin
Black Soldier Fly
in worm bin -1-
Black Soldier Fly<br>in worm bin -2-
Black Soldier Fly
in worm bin -2-

Master Gardeners' Help Desk:  Thank you for contacting the UC Master Gardener Program Help Desk with a question about strange creatures in your worm bin. And thank you for sending photos of them, making it easy to identify them. They are the larvae of the black soldier fly (BSF). 

You should remove the BSF larvae from the worm bin. They don't bite and aren't slimy or gross. If you know someone with chickens, they would probably be delighted to feed them to the hens. They're quite a delicacy (to the chickens) and some people raise them on purpose to use as food for a variety of kinds of animals.  
A large number of BSF larvae can be an indication that your composting conditions are not quite right. The worm bin may contain too much nitrogen or 'green' material and it may be too moist. Try adding more bedding to the bin, and bury food scraps with at least 4 inches of bedding. To keep adult BSFs out of your worm bin in the future, screen any holes with window screen. 
Here are links to two articles about black soldier flies you might find interesting: http://ccmg.ucanr.edu/files/115051.pdf and
Please let us know if you have more questions. 

Help Desk of the UC Master Gardener Program of Contra Costa County(SEH)
Notes: Contra Costa MG's Help Desk is available almost year-round to answer your gardening questions.  Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone:  (925) 608-6683, email: ccmg@ucanr.edu, or on the web at  http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ignore.edu/HortCoCo/ You can also subscribe to the Biog.

By Steve I Morse
Author - Contra Costa County Master Gardener