Molt nearly gone disasterously wrong, your mantis literally had to rip its arms off to finish its molt, or die. How long it takes to recover depends on the mantis and its age. As they get older they take longer between molts. The good news is, according to Dr. Roy, when a mantis looses both clubs it will put all its energy into molting and repairing. Figure at least 4 molts go really recover. You will need to feed your friend the best marine foods you can: Silversides, krill, scallops, sandeels, fresh snail (your mantis may not be able to crack a shell, but a gentle "tap" with a hammer will mitigate that problem), crab (again treated to a hammer massage). Soak it all in Selcon. You may even have some luck getting your mantis to eat canrivor pellets (Squirtle loved then when he was small), again soaked in Selcon or other vitiman soak.