Today I harvested the first of the prepupal black soldier fly larvae (Hermetia illucens) from this year’s colony. At this stage their instinct is to leave the food source and find a suitable place to pupate. I don’t know much about this part of the BSF life cycle so I want to find out first hand. I put the harvested grubs (larvae) into a closed container and I’ll be observing their behavior and changes, hopefully until the point where they emerge as adults.
When BSF grubs enter into their final stage as larvae they undergo some interesting changes. They go from a pale “grub” color to a dark coffee brown, and their mouth is replaced by a hook-like appendage to help them crawl in search of a good pupation site. They also empty their gut and excrete an antibiotic, a behavior which I find fascinating. A veterinarian friend of mine wonders if animals that eat the final stage grubs might benefit from ingesting the antibiotic.
Update MAY 31
Yesterday I placed about 15 prepupal BSF grubs into a one gallon container with some leaves and grass. If you click the photo above to enlarge it you can see a few of them. I added a handful of sand to one corner of the container and the larvae quickly buried themselves in it. One entered the sand but came back out and settled under a leaf.
I found a great poster by the Swiss Federal Institute of Aquatic Science and Technology (eawag), which outlines the BSF life cycle. BSF LIFE CYCLE
They’re just laying there…
*tap tap tap*
I spoke with Dr. Olivier and he said that sand isn’t the best material for a pupation site. He recommended using sawdust to house pupae. He also puts some in the BioPod collection bucket to help keep it dry. He told me about a hamster bedding that works well, I think it was Aspen Bedding.
My pupae are still pupating…..
Today I noticed adult BSF emerging from the pupae for the first time. It’s very possible that they started coming out before that but what can I say, I’ve been busy. I tried to photograph the process of the adults emerging but it happens very quickly. I checked on the pupae at one point and I noticed that an adult had it’s head out of the casing. I ran for my nearby camera and in the 20-30 seconds it took me to return the fly was already out and expanding it’s wings.