Sexual maturity occurs in female Lined Shore Crabs after roughly one year.  Males, however, can become fertile after only seven months. 

 

When fertile, females that are on the verge of molting emit a chemical signal called CRUSTECDYSONE, which attracts and stimulates males.  Because the exoskeleton proves as a tricky barrier to copulation, males can only mate with a recently molted, or soft-shelled, female. 

 

Egg-brooding females carry up to 50,000 eggs and brood up to two times per year.  They can be found from March to August in Central California, and from February to October in Southern Californian intertidal zones.  Peak months for reproduction occur in June and July.