Mexican red-knee tarantulas, like many tarantulas, grow slowly. Females wrap fertilized eggs in silk and carry the egg-sac between her fangs. After 1 to 3 months, the eggs hatch. Spiderlings molt every 2 weeks for the first 4 months, and less frequently after that. Males do not molt after reaching sexual maturity at 4 to 5 years of age. Females, though infrequently, continue to molt after reaching sexual maturity at 6 to 7 years of age. Molting removes any external parasites or fungus and provides new undamaged sensory and protective hairs.