May 18, 2012 – Timing Is Everything
QUESTION:
When a female German cockroach lays her capsule how long does it take to hatch? I have also heard that when a female German cockroach is killed her capsule can actually live. How long does it take for that capsule to hatch?
ANSWER:
According to studies quoted in the Handbook of Pest Control by Arnold Mallis, the German roach female will carry her egg capsule right up to the 24 hour period when the eggs hatch and the capsule pops open to release the new roach nymphs. If the capsule is dropped sooner than 24 hours before the nymphs are ready to emerge, of if that capsule is forcibly removed from the female, the new nymphs are unable to emerge. This may happen for a couple of reasons, but it boils down to moisture. The German roach has a very high need for water when compared with the other peridomestic species of roaches. This is why we tend to find these roaches harboring close to potential water resources, such as in kitchens or bathrooms. Their exoskeleton is thinner than that of other roaches and they may dehydrate faster. In addition, while she continues to carry her egg capsule the female is supplying it with moisture as well, so when it is dropped too early either the developing nymphs inside dehydrate or the capsule walls change and dry out and harm the ability for the nymphs to force it open.
View past Ask Mr. Pest Control questions.
When a female German cockroach lays her capsule how long does it take to hatch? I have also heard that when a female German cockroach is killed her capsule can actually live. How long does it take for that capsule to hatch?
ANSWER:
According to studies quoted in the Handbook of Pest Control by Arnold Mallis, the German roach female will carry her egg capsule right up to the 24 hour period when the eggs hatch and the capsule pops open to release the new roach nymphs. If the capsule is dropped sooner than 24 hours before the nymphs are ready to emerge, of if that capsule is forcibly removed from the female, the new nymphs are unable to emerge. This may happen for a couple of reasons, but it boils down to moisture. The German roach has a very high need for water when compared with the other peridomestic species of roaches. This is why we tend to find these roaches harboring close to potential water resources, such as in kitchens or bathrooms. Their exoskeleton is thinner than that of other roaches and they may dehydrate faster. In addition, while she continues to carry her egg capsule the female is supplying it with moisture as well, so when it is dropped too early either the developing nymphs inside dehydrate or the capsule walls change and dry out and harm the ability for the nymphs to force it open.
If the female roach dies while carrying the capsule that 24 hour period appears to be critical, so yes, the eggs may still be alive but they need to be fully developed and ready to hatch almost immediately. There have even been laboratory observations where the female was still carrying the egg capsule while the young roaches were forcing their way out of it, and even observations that the female helped her offspring to escape the capsule. Whether she was actually helping them or just tired of carrying them around and anxious to get rid of the little buggers is hard to say. The female carries that capsule around for a couple of weeks, and often will stay in seclusion during that time, so she can be pretty hungry once this period is over with and anxious to get out and find food.
The other common species of roaches (American, Oriental, Brown Banded) create the capsule and once it is fully formed the female drops it and then either glues it to a surface or covers it with debris. The egg capsule walls of these species are much thicker and better able to retain the moisture.
Over the decades I have been in the industry I have heard of attempts to create various kinds of hormones or other chemicals that would somehow interrupt the proper development of the eggs of the German roach. Perhaps there could be a way to reduce the number of viable eggs and nymphs within a capsule so that those that survive could not open it to escape. Perhaps there could be a way to cause the female to drop the capsule prematurely. Our IGRs do have some effect on this development, so the use of an IGR for roach management can be beneficial.
View past Ask Mr. Pest Control questions.
