CAUTION: LONG POST TO FOLLOW (got carried away haha)... nothing really new, but just putting things in perspective
I was just reading a quick study of temperature affects on darkling beetles. No species was given since this was not the actual scientific study, but was using graphs from one. The first thing I noticed is that the temperature of the litter is more important than the air. This makes sense since that is where they live. So using a reptile heater or something like some people here are doing seems to be a great idea. The second thing I noticed is that temperatures just below 70F are quite different from those around 80. The difference between 80 and 90 and 100F were not as drastic even though there were definite differences. At 68F, the life cycle is much longer and as a result the survival rate is much lower. Like I said, the species was not given and I am pretty sure this is not the ones we grow, but the logic still stands. When the litter is cooler, it takes longer for the eggs to hatch which increases the likely hood that the egg won't hatch at all. But that is just the start. The cooler temperatures also increase the time in the larval stage (mealworm stage). This has a large impact on survival rate.
Besides temperature, one thing that sticks in my mind is the difference the starting colony number makes. I knew that it made a difference, but never really calculated it. In my mind I am thinking in terms of increasing the number 10 fold over the life of the beetle. Like I said, I never put numbers to it. But even with my original estimate, starting with 50 mealworms yields 500 vs starting with 1000 mealworms yielding 10,000. Boy, was I in the wrong mindset. Now that I saw some real numbers applied in this article, not only were my numbers off, but this is really a logarithmic difference. The article says that on average, you can expect 5 eggs per day from a female in the higher temperatures (over 95F). If you start with enough mealworms to yield 100 beetles after the mortality rate, let's say 50 are female. That means that 250 eggs are laid a day. After 30 days, that is 7500 eggs. After 60 days, that is 15,000 eggs. After 90 days that is 22,500 eggs. Now let's look at the same numbers if you had enough to end up with 200 female beetles (so 400 beetles in our example). 1 day = 1000 eggs. 30 Days = 30,000 eggs. 60 days = 60,000 eggs. 90 days = 90,000 eggs. This is just egg production. You would then have to factor in the mortality rate of the eggs and the larvae. But you would also have to factor in any larvae becoming a beetle and laying their own eggs. But I'lll stop here before I make this even longer.
So now I am wondering the best way to get my temperatures up. I would say anything over 80F would be ideal. Right now they are at around 70 (I haven't checked for a bit). I don't really want to use a space heater and the reptile pads that attach to the outside of the cage give a large range of possible increase for the product (between 2 and 8 degrees F). Not worth it for 2 degrees, but maybe for 8. However I imagine there are ones out there that might be better. I also can't wait for Spring... or Summer
