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 environment as well as identify and solve nutritional, general health, and other issues when they arise rather than going months or years without knowing a problem even existed. In short: knowing what’s normal can help you keep a roach colony healthy and a breeding project on track.
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 variation is common, even “normal”. However, severely inadequate conditions can also vary the number of instars. This type of variation will lead to poor roach health and slowed growth.
However, a change in the number of instars will not be a factor in a well-maintained captive Dubia roach colony. It takes extreme conditions to change them. 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.
Conversely, when starting from a position of inadequacy, 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 needs improvement. Knowing this can help you maximize the growth of a Dubia colony and head off many of the problems that plague them before they develop.
Of course, more is not always better. There are natural limits beyond which providing more of something has no effect, and may have adverse effects. Temperature is one example. Moisture is another – particularly with captive colonies.
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 round the days to weeks because there is significant variation among roaches. This is true even with roaches reared together under 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, but this would be practically useless. There is simply too much variation. Many factors affect Dubia roach size and weight, including hydration, reproductive status, growth cycle, and the quality and amount of food they eat. 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.