We often get asked if black soldier fly larvae can be chicken's only source of food. To put it simply, the answer is that they probably can, but this kind of diet may not be ideal, neither for chickens nor for your wallet.
Chickens eating only dried larvae is akin to us humans eating a meat only diet. There are some people who are strong proponents of a meat only diet, but generally speaking there are just not enough studies looking at the long-term impacts of it. We do not really know what nutrients we are missing out on and may have to supplement with if we switch to a meat-only diet. Perhaps if you are getting your chickens ready for a bodybuilding competition, they may benefit from such a diet to get shredded but since such a discipline has not been established yet, you might want to hold off for now.
The other side effect of feeding chickens only black soldier fly larvae is the fact that such a diet would be much costlier than using a good layer feed. And you can think of this problem through the lens of humans consuming an all-meat diet. Ultimately, not all of the protein consumed can be used to pack muscle, or build tissue, or even produce eggs. Some of the protein will end up being used as a source of energy, something much cheaper carbohydrates could've been used for. So in that sense, the real reason why you shouldn't feed your chickens an all black soldier fly larvae diet isn't because it would be more expensive but because you just wouldn't be able to have any marginal improvement in chicken's health, egg production, or any other aspect of life, while at the same time you would be spending more money. tl;dr spend more and get the same result.
Truth be told, chickens (and we are talking free-range chickens here) are pretty much self sustaining as long as you are not raising them in Antarctica or Sahara desert, and this is not because of Antarctica or Saharan weather but the lack of vegetation and readily available sources of food. Chickens will finish off your food scraps, whatever they may be, since they are one of the least picky eaters you can find. Just like humans, chickens will also feel a mineral deficiency and may start finding interesting stuff in your garden to nibble on if they lack certain minerals, like Calcium.
But at the same time, survival is not the same as optimal living. Rarely anyone buys chickens with the idea of simply maintaining them alive. It would be both unethical and also it would be hard to reap any benefits from raising chickens. Sheer survival is sub-optimal living and this will affect the chickens in that they may not end up producing as many and high quality eggs, or may not reach the size they are genetically predisposed to get to - in case you are raising broilers. If you want your chickens to live a comfortable life and award you for taking care of them, you should get more involved when it comes to the type of feed to be used, treats and supplements. The same goes for other perks that go beyond nutrition, like heating, a nice chicken coop to keep them well protected against predators, etc.
You may have expected a slightly different answer from the makers of Supreme Grubs black soldier fly larvae but we believe your chicken's welfare is priority number one for us. To help your chickens stay happy and healthy, choose a good comprehensive feed to satisfy most of the basic nutritional and mineral requirements, but add some variety and supplement their base feed with treats to ensure your birds get all they need to reward you with plentiful and high quality eggs.