Expert: Walter Hintz - 4/23/2006

Question
I asked an expert in here and he is on vacation!
I don't know if my question category is right, but the questions came up while wrting a report for my biology assignment, so you might help me!

I was looking for an answer, and I found this site! I read a Q&A posted on this site : http://experts.about.com/q/Accuweather-2546/perceived-temperature-1.htm
It said that in cold weather, if there is no wind, you feel warmer in humid condition.
Is it because the transpiration rate is lower in humid condition?
And this one might seem a bit of a weird question...:-) If someone who has been in room temperature goes in to a cold room, which room will feel colder at the start, dry & cold room or humid & cold room?


On how I came to ask those questions: I am doing an experiment(high school assignment) on the effect of temperature on humidity response in woodlice.
Woodlice loves humid condition as they die from dessication in dry condition and they like temperature around 15 to 20 degrees celsius.
The result turned out, in 5 degrees, they first went to dry chamber and started getting back to the humid chamber. There was no striking preference in 15 degrees.
I was expecting for them to show no preference to any of dry or humid side in 5 degrees, because I thought that the relative humidity in low temperatures does not really affect the transpiration rate or the perceived temperature.
However if one feels warmer in more humid place in low temperatures, that would explain why woodlice preferred the humid chamber in 5 degrees.
I also thought that humid & cool air might be felt colder than dry & cool air at first, because woodlice went to the dry chamber when they were first released.
Hmm... my experiment might be wrong because I only did 5 trials for each temperature and also because I counldn't keep the temperature constant all the time.

Excuse my poor english, and Thanks! Wish you well from New Zealand!

Answer
Hi Semi. First of all it is true that evaporation is less in humid conditions. Please note that I refer to evaporation as transpiration is a plant function and does not occur in animals.
 In the US we call woodlice sowbugs or pill bugs.  I have been piecing together your data as you present it. Sowbugs lose water from evaporation and through respiratory organs.  Unlike insects they do have as much chitin in their exoskeleton and are more prone to water loss through evaporation. The greater the humidity the less the water loss from evaporation.  It is also correct that temperture ha san effect upon water in the air.
 I do not believe that you can apply the behavior of invertebrates to the response of mammals to changes in humidity and temperature. Report your data on the behavior of the sowbugs without inferences to how you and I feel.