If you raise tenebrio molitor as feeders, read this...

Last year, I started a mealworm colony to feed my pet frog. Since I had the intention of raising them for food, I decided I wanted to see exactly how many mealworms I would get from the first generation of mealworms.

I used mealworms from Petsmart, the exact brand name is timberline. The substrate they were packed onto wasn't a very nutritious substrate so I picked up some generic oats (the package said 3 grain oats) from a local grocery store. I mixed a lidful of calcium and vitamin powder into the oat substrate for the mealworms.

After the mealworms emerged from the pupa, I seperated twelve individuals. These were kept in three groups of four. These individual beetles were captured during the mating process so it is a known fact that there were two males and two females in each of these groups. The beetles were kept at room temperature (70-75 F) in a darkened closet in the timberline mealworm containers in the oat substrate the mealworms were raised in, with one difference from their brothers and sisters. There was no vitamin powder in this substrate. I kept one container seperate as a control. No mealworms developed in this container, so we are to assume that there were no unhatched eggs in the substrate.

I waited until my colony of mealworms had just started to pupate before counting the larvae. In the first container I counted, there were 17 mealworms, ranging in size from half a centimeter to one centimeter. In the second, there were 18 mealworms about the same size. In the final container, I counted 34 mealworms, ranging in size from half a centimeter to one centimeter.

The average number of mealworms per pair of mated beetles was 12 larvae for every pair mated for the first generation.

Since the second generation was raised on better food, I expect to have bigger brood sizes.

Anyone else think this is kind of small?

Your post is pretty old so this may be impertinent by now, sorry, just got on this forum. In my opinion, and according to my extensive experience raising Tenebrio molitor, Zophobas morio, Galleria melonella, Gromphadorhina portentosa, etc., I have some tips. First, I commend your high degree of record keeping, use of control, and consideration of many cultural conditions. That being said I think you are WAY overcomplicating the culture of mealworms. They are very easy to raise. This is what I do and I have raised literally hundreds of thousands over the last 14 years. Low, wide Rubbermaid or Sterilite sweater box type storage container with lots of holes drilled, punched or melted into the lid (they can't climb). Floor space is more important than height so make it low and wide. Substrate=plain old instant oatmeal in the cardboard tube. No need to gutload with any vitamin powder or supplements. A few veggie scraps here and there (carrot, potato, apple work well. skip broccoli and spinach as they are high in oxalic acid which binds calcium. not as important in T's because too much calcium can be hazardous to them anyway but if you raise your mealworms for other critters it's a good thing to know). I then lay a single ply of kitchen paper towel on the top and mist it LIGHTLY. This will provide a water source. The grubs will eat the paper and ingest the water. Be VERY careful not to let it get funky inside. If you see condensation on the inside of the box it is way too wet. Leave the lid off for a few days to dry it out a bit. These guys subsist on little water. I have never bothered to try to keep them dark. Although this grain beetle likes darkness (hence the common name, Darkling Beetle), you don't need to worry about it, they will burrow enough to cover this. I clean the container once every few months in the following manner. Get a critter keeper, use a fine mesh wire kitchen strainer or tea diffuser, scoop the whole mixture and dump into strainer over the critter keeper. The frass, tiny eggs, and tiny larvae will fall through mesh. Save this, it's your future generation. The macroscopic particles (grubs, beetles, viable food and carcasses) will stay in strainer. Put these back in your main colony. The finer particles I mix with just a shaking of the oatmeal and watch the eggs and small grubs grow. When they pupate I pick them out and dump them back into main colony. Now what you have in your second container is just frass (insect feces). This is mostly indigestible cellulose fiber and maybe some ammoniacal nitrogen. Great, dump it on your garden for essential plant nutrients and to improve soil structure (not in a vivarium or houseplant as it will likely cause fungal and bacterial growth). I have produced so many of these insects in this manner that I often give them away or dump them on my compost pile (also great fishing bait, food for psittacines, sugar gliders, etc.). Good luck all, be well.

That was probably the most helpful 9 years late reply I've ever read on this forum. I really am going to try this method. I've watched videos and it always seems more complicated than makes it worth the time.