Thus a pair of brown rats can produce as many as 2,000 descendants in a year if left to breed unchecked. (A rat matures sexually at age three to four months.) An average rat's life span is two to three years.5 A rat can tread water for three days and survive being flushed down the toilet.hus a pair of brown rats can produce as many as 2,000 descendants in a year if left to breed unchecked. (A rat matures sexually at age three to four months.) An average rat's life span is two to three years.
Late lice. The common head louse, Pediculus humanus capitis, may take as long as 14 days to hatch. Gilles San Martin/Wikimedia Commons. Hereâs some lousy news for parents of itchy-headed kids: Lice eggs can take 2 weeks to hatch in human hair, making standard 7-day delousing treatments ineffective in some cases.
1 Head lice cling to hairs but stay close to the scalp which they feed off. 2  Head lice lay eggs which hatch after 7-10 days. 3  It takes about 10 days for a newly hatched louse to grow into an adult and start to lay eggs. 4  Nits are the empty white eggshells which are left when the lice hatch. They are about the size of a sesame seed (the seeds on burger buns). 2  Head lice cling to hairs but stay close to the scalp which they feed off. 3  Head lice lay eggs which hatch after 7-10 days. 4  It takes about 10 days for a newly hatched louse to grow into an adult and start to lay eggs.