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.