Dubia roach growth is predictable, and you can use this to your advantage. Knowing their growth rate can help prospective home breeders plan ahead and set reasonable expectations for their colony’s future. Because Dubia roach growth depends on environmental conditions, knowing how fast (or slow) they should be growing can also help you fine-tune their current environment as well as identify and solve nutritional, general health, and other issues as they arise rather than going weeks or months without even knowing a problem existed.
In short: knowing what’s normal allows you to track their progress and address potential issues before they linger too long and turn into real problems with real consequences.
Knowing and understanding the basics
Dubia roaches have seven growth phases between molts called instars hard-wired into their physiology. While the number seven is fixed, environmental conditions can affect instar length. This kind of variation is common, even “normal”. However, at some point inadequate conditions can vary the number of instars. Rather than normal variation, this variation leads to poor roach health, slowing growth, and reduced productivity.
However, a change in the number of instars due to seriously inadequate conditions is not typical in well-maintained captive Dubia roach colonies. The conditions really need to be extreme for them to change. Some of the factors that may increase the rate at which Dubia roaches complete instars (external link) or increase the number of instars if they are extreme enough are low temperatures, poor diet, starvation, low humidity, injury, and an increase in daylight hours.
Using expectations to find problems
Conversely, when starting from a position of inadequacy, improving these things can increase the rate of growth. This is of particular importance to Dubia breeders, and is the point of this post.
A dip in growth signals less than ideal conditions. It means something is wrong and needs improvement. This knowledge can help you maximize the growth of a Dubia colony and head off many of the problems reported by roachkeepers.
Of course, more is not always better. There are natural limits beyond which providing more of something has no effect, and may even have adverse effects. Temperature is one example. Moisture is another. This is particularly with captive colonies.
Instar completion in weeks
The following are the average number of weeks Dubia roaches take to complete their seven instars. This is based on our experience with colony temperatures between 80ºF & 90ºF.
Average time to complete instar. (instar number: weeks)
This means Dubia roaches go from birth to adulthood in about five months. We can round days to weeks because there is significant variation among roaches. This is true even with roaches reared together in the same conditions. In fact, individual variation of the time from birth to completion of the final instar can vary as much as two weeks.
Unlike instars, the rate Dubia roach body size and weight increase over time are difficult to predict. We could assign a range of sizes and weights, they are so varied that this would be practically useless. There’s just too much variation. Many factors affect Dubia roach size and weight, including hydration, reproductive status, growth cycle, and the quality and amount of food consumed. Some of these have very little or no relation to the actual Dubia roach growth rate. They may also vary weekly, and sometimes even daily. A hungry roach can double its weight with food alone, so weight is a poor measure of progress.
Having said this, there is a size-related measure of Dubia roach growth that is relatively constant and predictable. However, it has little practical application for feeders or breeders. It involves measuring the width and length of the roach’s head at the beginning of each instar, then plotting changes over time. For Dubia roaches, this growth rate is a constant 1.25, which means each instar is marked by a 125% increase. Incidentally, this rate is standard across many insect species.
Read more: Deep dive into Dubia roach breeding »
Understanding expected Dubia roach growth rates, how to measure them, and how to use this data to troubleshoot in case there’s a diversion from the expected norm can be a significant help Dubia roachkeepers in their breeding projects. The greatest advantage is that when implemented correctly, tracking actual and expected growth can not only help maximize productivity and reproductive efficiency but potentially even alert to problems early enough that any lasting negative consequences can be entirely avoided.
Have a question?
If you have a question, please feel free to ask! You can use the comment form below.
I just had a female roach give live birth yesterday, only 15 made it. The others were still in their egg sack dead.
Low nymph survival happens sometimes. It’s impossible to diagnose the issue based on this information alone, so start by checking the conditions and work to move them as close as possible to the ideal. On average, the closer the environment is to perfect, the more baby roaches will survive. Check temperature, humidity, etc., as well as nutrition. Make changes if anything is off and observe the results.
I’ve had a colony for a while now and there are tons of babies that I finally separated. But they seem to not be getting any size to them. Some were born 2 months ago or more and they are still are way smaller than the average rollypolly. Do you have any pointers to identify issues I may be having? Also how can you tell when a female is gravid?
As with most Dubia roach problem solving, start with the basics: Temperature, humidity, food, light/dark, etc. You have to get those right. Regarding lack of growth, the order of importance might be something like (1) temp, (2) food, (3) light/dark etc. When you have everything right, they should grow as intended.
The abdomens of gravid females tend to elongate, but food will tend to do that too, so an elongated abdomen is not a reliable way to tell whether or not they’re gravid. It’s a sign, but not an absolute.
I started a Dubia colony a few months ago and my first nymphs started to become adults about two weeks ago. I have noticed that almost all of roaches reaching adulthood are male. Only about one out of 12 are female. Do the males complete their final instar sooner than the females? I have just been feeding off the extra males, but at this rate, my colony is going to be growing very slowly.
If males emerge as adults faster than females, the time difference is probably going to be less than two weeks.
Keep an eye on that, but it seems more likely that if there is in fact a real difference in the male:female ratio in your colony, the cause is some external factor. This could relate to stress, nutrition, or both. Unfortunately, nearly everything you do is going to affect one or the other. Fortunately, you control all of them.
The best suggestion is to make sure your colony is up to standards regarding conditions and diet, and keep an eye on the male:female ratio. The difference you’re seeing could just be caused by chance if your colony is small enough. But if it’s not chance, the problem will persist and the best you can do is get their diet and housing right and hope that something you change resolves the issue.
In a healthy Dubia roach colony, the sex ratio is roughly 50/50. If you get all the conditions right, you will have a healthy colony. Alternatively, it would indeed take a while to build a Dubia colony if something about the conditions causes you to get only female for every 12 males, so again – if what you’re seeing is real – it’s probably worth some effort to resolve.
I’ve had my colony for a while now, but I’ve only seen Dubias that have gotten up to the 5th or 6th instar and 60-70 of the 200 something adults that I have died. Should I be getting worried at this point or give them more time to grow to the adult stage? I was thinking about buying some more adults so they didn’t die off completely since they’re kind of old now.
Most of your Dubia should reach adulthood. If 30% are not, there is a problem. The possibilities are many, but you may want to generally consider things like diet, temperature, and humidity. Our article about breeding breed Dubia roaches can provide more in-depth information that might help you diagnose and resolve whatever issue might be happening.
Adam M. says
What instar stage would you consider the average medium feeder?
Very generally, “average” is probably in the 4th or 5th instar, so that puts it in the 2.5 to 3 month range.
I’m confused about the instar periods for each growth stage. Your text says that Dubia roaches go from birth to adulthood in about 5 months, which sounds about right to me. But if you add up the weeks listed for each instar stage, it totals 73, which is about a year and a half. Can you clarify this for me? Thank you.
I don’t think you are supposed to add them up. The “week number” should represent the age of the roach – the time that has passed since the roach was born, not since the last shedding.
The comment above is correct. The week number is total time from birth to instar completion and not the time spent in each phase.