Deer flies generally find temperatures below the low 70s Fahrenheit too cold for sustained and regular flight activity. While they may be present in cooler conditions, their ability to fly effectively and consistently is significantly diminished below this range.
Understanding Deer Fly Activity and Temperature
Deer flies are highly dependent on warm temperatures for their characteristic flight behavior. Their activity peaks during warmer parts of the day and year, typically from late spring through summer. As temperatures drop, their metabolism slows, impacting their ability to fly, hunt, and reproduce.
Even within the low 70s Fahrenheit, conditions may not be optimal for these biting insects. While the low to mid-70s are considered the minimum temperature range to permit a sustained period of flight, the low 70s alone may not provide truly favorable conditions for deer flies to regularly fly, especially if combined with high humidity which can also influence their discomfort. For these insects to be consistently active and troublesome, temperatures typically need to be warmer.
Factors Influencing Deer Fly Activity
Beyond a simple temperature threshold, several environmental factors influence how active deer flies are:
- Temperature: As noted, temperatures below the low 70s Fahrenheit significantly reduce their flight capability. Their peak activity often occurs in much warmer conditions.
- Humidity: High humidity, even in seemingly warm temperatures, can contribute to uncomfortable conditions for deer flies, potentially reducing their regular flight activity.
- Time of Day: Deer flies are most active during the warmest parts of the day, typically from late morning to late afternoon.
- Season: Their populations and activity are highest during warm summer months, typically declining rapidly as autumn approaches and temperatures drop consistently.
- Light Conditions: They prefer sunny conditions and are less active in shade or during overcast weather.
When Are Deer Flies Most Active?
To better illustrate the temperature-activity relationship for deer flies, consider the following general guidelines:
| Temperature Range (Fahrenheit) | Deer Fly Activity Level | Notes |
|---|---|---|
| Below Low 70s | Limited to None | Too cold for sustained or regular flight. Deer flies will be largely inactive or absent. |
| Low 70s | Possible, Not Regular | While sustained flight may be possible, it is not considered favorable for regular flight. Activity will be reduced compared to warmer conditions, and they may be less persistent. |
| Mid 70s and Above | Favorable / Peak | Ideal conditions for sustained and regular flight. This is when deer flies are typically most active, persistent, and problematic. Activity can increase with rising temperatures into the 80s and 90s. |
For more information on insect behavior and environmental factors, you can consult resources from university extension offices or entomological societies, such as those found on University of Maryland Extension.
