What can be an effect of a lack of blood meals in certain fly species?

The correct answer highlights that a lack of blood meals can lead to lower survival rates in certain fly species that depend on blood for nutrition and reproduction. Many blood-feeding flies, such as certain species of mosquitoes and tsetse flies, rely on nutrients from blood meals to mature their eggs. Without these vital meals, they may not attain the necessary resources to grow, reproduce, or sustain their metabolic processes effectively. This can lead to increased mortality rates among those individual flies, as they cannot complete their life cycles or maintain energy levels.

Contextually, flies that do not depend on blood for their survival or reproduction may not face the same negative impacts from a lack of blood meals. The other options, such as increased vulnerability to predators or requiring more energy, generally do not align with the nutritional needs and life cycle dependencies of blood-feeding fly species.