During which seasons are cluster flies most abundant?

Cluster flies are most abundant during spring and fall due to their seasonal life cycle and behavior patterns. In spring, as temperatures rise, adult cluster flies emerge from their overwintering sites to seek out suitable environments for laying eggs. These flies are known to be particularly active during this time as they look for food sources and breeding opportunities.

In the fall, cluster flies begin their search for warmer shelter to overwinter, which leads to increased sightings as they invade structures in search of warmth. This seasonal migration results in a notable increase in their population in the fall, making both spring and fall peak times for their activity.

During winter and early spring, cluster flies are not notably active or abundant, as they tend to remain in a dormant state, making these seasons less populated for them. Likewise, while they can be present in summer, it's not the primary season for their abundance as they are less noticeable during those months. The notion of them being active all year round does not hold true, given their distinct seasonal behaviors.