To establish black soldier fly larvae (BSFL) you first need to attract the adult (winged) females so they can lay their eggs. To do this you need to bait them with some type of food.
Types of food for baiting BSF
You may use almost any food scraps, but I’m experimenting with different types to see which are the best. To find the bait the flies will need to be able to follow a scent trail, so items like vegetable peels or bread might not be the best choice. You may not attract the BSF right away so choosing a type of bait that won’t spoil too quickly may be a good idea. When I started a new colony this year I put out dry dog food (slightly moistened), used tea bags, refried beans, cottage cheese and coffee grounds. The teabags helped hold in moisture and the BSF like to lay their eggs on paper. I’ve noticed that the larvae seem to like coffee grounds so I thought they might be good for attracting adults. I kept this bait outside in fairly warm weather for two weeks and it never did get too nasty and it worked pretty well also. I think it’s a good idea to keep the bait moist for two reasons; the smell will be a little stronger (better attractant) and any eggs may develop more effectively.
This year instead of putting my BSF bait directly into the BioComposter I tried putting out four individual bait boxes (see photo above). I made them by cutting the ends off of 12 pack soda cartons. Since I added water to the bait everyday it would have been a good idea to reinforce the bottoms with tape, but they held up just long enough. One reason I tried these boxes was to make it easier to swap out the bait if it spoiled too much. The main reason I tried it was so that I could easily move the bait to different areas. I think one of the best places I found was near a garbage can that was a little past the point when it should have been picked up. I moved the boxes into a closed container at night because the BSF aren’t out then. In fact, I’ve rarely seen one laying eggs before noon, they seem to be active during the hottest part of the day. Maybe that will change as we move into summer.
Once you have established a balanced colony of BSF larvae the number of houseflies near your colony will be dramatically reduced. Most likely you will have to put up with them until then. Either way it’s wise to wear latex gloves when handling the boxes. With an established BSF colony I usually just wash my hands immediately after working with them. Unlike houseflies, black soldier flies aren’t associated with the transmission of disease.
After about a week I was seeing a good number of BSF laying eggs in the bait boxes so I moved them all into my BioComposting unit. Two weeks after setting out the bait I removed the bait boxes. The photo below shows my progress at that point.