Applying Heat to Test Tubes?

[MarketTree]

I currently have 1 Tetramorium, 2 Camponotus Pennsylvanicus and 6 Lasius Neoniger queens, all in test tubes. I know that the brood would develop better if I were to apply heat but I don't want to accidentally cook these girls.

I have a spare Zoo-Med under-tank heating pad, used for reptile tanks. Would it be appropriate to put this heating pad near or under the test tubes, or would that be too much heat?

Also, would any of my 3 species benefit specifically from more or less heat?

Thanks a lot!

[Mandelstam]

If you have a thermometer with a separate sensor you could test out the setup with the heating pad on an empty tube and see how hot it gets and maybe play around with raising/lowering the tube (or with the thermostat if you have one) to reach the optimal temp?