How can you tell if a cockroach egg case will still hatch?
If it’s a German cockroach egg case and there is no German cockroach attached, it’s either very old and already hatched or it’s almost ready to hatch. The German roach female carries her egg case with her while it is developing. She finally deposits it in a hidden area just 12 to 24 hours before hatching. Sometimes however, when the female is stressed by pesticides, she may drop her egg case early before it can survive and hatch. Other cockroaches deposit their egg cases shortly after they are formed and many days before hatching.
That still doesn’t answer your question. Yes, you can usually tell whether an egg case has hatched by looking at it closely. Regardless of the species of cockroach, if an egg case is split along a side seam, the nymphs have already emerged. When the embryos are fully developed, they exert pressure that splits the egg case open along the top seam. If the egg case looks plump and full, it’s probably a viable egg case and is going to hatch. If it has dents or depressions in it, it means that the nymphs inside have either hatched or they have dried out, and hatching is unlikely.
What’s inside the egg case? – Inside a cockroach egg case, the eggs are arranged side by side along the length of each half of the egg case. Inside a German cockroach egg case, you would find 30 to 48 nymphs developing, half on each side (see illustration). Each indentation on the outside of the case outlines an egg compartment on the inside.
The hatching time for a cockroach egg case varies depending on the species, the temperature, and the humidity. A German cockroach egg case can hatch in 18 days after it is formed, while the egg case of the Brown banded cockroach can take up to 75 days to hatch.