Dubia = Cannibals?

[JeffreH]

There are some roaches in the Blaberus genus that seem to be more prolific under higher population densities; which is often a rarity in most organisms. Overcrowding, pheromone bombardment, intraspecific competition for resources, etc all add some amount of stress to cockroaches (and most any other species, for that matter). This stress can encourage things like small body-size and cannibalism in your bin.

Blaptica dubia will cannibalize their offspring or freshly molted individuals if the need exists. How dense is you population in the bin? The need to separate nymphs isn't too great, but you will notice some population benefit if you take the time to do so as newborn nymphs are the most delicate of all instars. Cannibalism shouldn't result under the conditions you're providing so long as there is plenty of space. And while B. dubia can be cannibalistic, it isn't going to make a significant impact on your colony. Maybe a couple of nymphs per litter on average... these guys really aren't a major threat to themselves at all. Compare a B. dubia colony to an E. posticus (orange head) colony under the same conditions and you will be shocked at just how cannibalistic a different roach species can be.

The other thread you were referring to I think discussed keeping two separate species together; G. portentosa and B. dubia. The prior will more readily cannibalize cage-mates for the same reasons I've mentioned in the first paragraph. The two can be kept together with success, and can even maintain decent fecundity, but they often need more attention in the resources department to discourage interspecific competition. I've heard that cramped conditions and excessive pheromone production can sometimes have negative effects, but I don't have the data to back this personally. The ticket is adequate space, food, and likely most importantly, moisture.

If it makes you feel any better - I have a couple of B. dubia bins that I only get around to feeding once a week or so...maybe once every couple of weeks. I'm allowing for some self-thinning while there is a surplus in other cultures. Despite being fed and watered with extreme infrequency, the colonies are still viable and producing offspring. Adults are suffering and clutch sizes aren't as high, but the population is at least stable. Given the care you are providing to yours, I wouldn't be too concerned ; ) If you think things are too crowded, consider setting up another bin. Here is an example a bin that is too crowded that I needed to separate out: