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I study insects that are leaving freely on my campus. The campus weather station has two different measures of temperature, the Dry Bulb Temperature and the Dew Point Temperature. Which one is the most relevant when studying insects? Are they very different? In other words, can you state the main differences between the two that are relevant when studying insect biology.

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Insect development and activity are strongly associated with dry-bulb temperature. Development rate is usually predicted using degree-days (Links here: http://ipm.ucanr.edu/WEATHER/ddconcepts.html and https://entomology.ca.uky.edu/ef123). Basically this takes advantage of the nearly linear relationship between development rate and temperature in almost all insects (in some the type of food available can also be limiting). At temperatures above a certain threshold -- usually around 50 F or 10 C -- the warmer it is, the faster development will take place, up to a certain temperature cut-off above which development is drastically slowed (varies widely from species to species).

Insect activity is also strongly associated with dry-bulb temperature. In general most insects cannot fly at temperatures much below about 50 F or 10 C. They cannot generate energy fast enough at lower temperatures. The species that do fly at lower temps are generally Hymenoptera or Lepidoptera that use group or individual muscle movement to generate heat. Those that do fly in cooler weather or at night are often covered with fur or hair, which allows them to retain more of the heat generated by their flight muscles.

Wet bulb temperature generally relates to relative humidity, which has little to do with insect activity except in extremely hot, dry environments, wherein insects will be much more active during higher relative humidity (as it helps them retain more moisture) times of day such as morning or evening.

I hope this helps.

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    $\begingroup$ By wet bulb do you mean dew point? On Wikipedia it is said that those two are different. $\endgroup$ – Nakx Apr 12 '18 at 10:21
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    $\begingroup$ Sorry, no. They are different, but they both relate to the same idea, of describing the moisture content of the air. The Dew point temp is always somewhat lower than the wet bulb temp, as wet bulb temp is in dynamic equilibrium between warming from air temperature (measured by dry bulb temp) and adiabatic cooling via evaporation from the wet bulb. Dew point temp is the temperature at which relative humidity is 100%. Insect activity and metabolism are not strongly affected by humidity (except as I noted above) so it is the dry bulb temperature that is significant, in any case. $\endgroup$ – Bugmo Apr 12 '18 at 23:19

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