"N. americanus" and "A. duodenale" eggs can be found in warm, moist soil where they eventually hatch into first-stage larvae, or L1. L1, the feeding noninfective rhabditoform stage, will feed on soil microbes and eventually molt into second-stage larvae, L2, which is also in the rhabditoform stage. It will feed for about 7 days and then molt into the third-stage larvae, or L3. This is the filariform stage of the parasite, that is, the nonfeeding infective form of the larvae. The L3 larvae are extremely motile and seek higher ground to increase their chances of penetrating the skin of a human host. The L3 larvae can survive up to 2 weeks without finding a host. While "N. americanus" larvae only infect through penetration of skin, "A. duodenale" can infect both through penetration and orally. After the L3 larvae have successfully entered the host, they then travel through the subcutaneous venules and lymphatic vessels of the human host. Eventually, the L3 larvae enter the lungs through the pulmonary capillaries and break out into the alveoli. They then travel up the trachea to be coughed and swallowed by the host. After being swallowed, the L3 larvae are then found in the small intestine, where they molt into the L4, or adult worm stage. The entire process from skin penetration to adult development takes about 5–9 weeks. The female adult worms release eggs ("N. americanus" about 9,000–10,000 eggs/day and "A. duodenale" 25,000–30,000 eggs/day), which are passed in the feces of the human host. These eggs hatch in the environment within several days and the cycle starts anew.