Which characteristic of midge larvae makes them sensitive indicators of environmental health?

Midge larvae are sensitive indicators of environmental health primarily due to their requirement for clean, oxygen-rich water. This characteristic means that they thrive in environments where the water quality is high, and oxygen levels are sufficient. The presence of midge larvae in a water body is often indicative of good environmental conditions because they cannot survive in water that is heavily polluted or low in dissolved oxygen. Their sensitivity to these environmental conditions makes them valuable bioindicators for assessing the health of aquatic ecosystems.

In contrast, the other characteristics listed do not relate to their role as indicators of environmental health in the same way. For instance, while some organisms may grow in polluted water, midge larvae specifically are known to struggle under such conditions. Being able to survive low temperatures and having a short lifecycle are advantages for survival and reproduction but don't directly correlate with the assessment of water quality or environmental integrity.