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.
Lice eggs hatch within 1 to 2 weeks after they're laid. After hatching, the remaining shell looks white or clear and stays firmly attached to the hair shaft. This is when it's easiest to spot them, as the hair is growing longer and the egg shell is moving away from the scalp. Adult lice and nymphs (baby lice). The adult louse is no bigger than a sesame seed and is grayish-white or tan. Nymphs are smaller and become adult lice about 1 to 2 weeks after they hatch. If head lice is not treated, this process repeats itself about every 3 weeks.