Monthly Temperatures and Wing Centroid Sizes of Fruit Fly Specimens
| Month | Average high (°F) | Average low (°F) | Average male wing centroid size (mm) | Average female wing centroid size (mm) |
|---|---|---|---|---|
| May | 73 | 50 | 1.98 | 2.27 |
| September | 80 | 54 | 1.98 | 2.27 |
| October | 67 | 44 | 1.98 | 2.29 |
| July | 87 | 62 | 2.02 | 2.31 |
Drosophila (fruit flies) have generation times of – days, so seasonal changes in humidity and other environmental conditions can drive seasonal fluctuations in body size from one generation to the next. To test this idea, a team of researchers recorded the average monthly temperatures and measured the average wing centroid size (a proxy for body size) of male and female fruit fly specimens collected in four different months. The researchers concluded that the flies’ body size fluctuated seasonally; this conclusion is best supported by the observation that __________