At time one, 50 butterflies were captured and marked with paint. Two days later, 100 were captured and 10 were previously marked. What is the estimated population size?

A) 100
B) 500
C) 1000
D) 5000
E) 10,000

The estimated population size can be calculated using the Lincoln-Petersen Index: $N=\frac{C_1\times C_2}{R}$ , where $N$ is the estimated population size, $C_1$ is the number of individuals captured and marked in the first capture (50), $C_2$ is the number of individuals captured in the second capture (100), and $R$ is the number of marked individuals recaptured in the second capture (10). Plugging in the numbers: $N=\frac{50\times 100}{10}=500$ .