I have been working in electronics for 30 years and as an engineering tech for the past 20 and I have to tell you, this idea of yours of using what you call a remote thermometer when the fruit flies lives are at stake is really scary. Why ? Do you know the principle or should I say theory of operation of one of the interferometers ? They are based on the emisivity of the surface they are pointed at.
They will not read the same temperature for two different types of reflective surfaces. Have you calibrated it with a thermocouple ?
You should be using temp sensors, like DS18B20s or at least LM35s . I recommend you buy the thermocouple breakout board from
Adafruit and a thermocouple immediately
and throw your "remote sensor" in the trash, or at least calibrate it with an accurate contact sensor like a adhesive thermocouples from OMEGA. Unless you can conclusively say that the reading on the remote sensor matched the thermocouple in contact
(taped to the glass with Kapton tape) to within 3 %, you shouldn't be using it. I have not many people who are not engineers who
understand the drawbacks of that kind of sensor.