I use a human heating pad underneath my dubia bin, it gets the temp inside high enough to encourage breeding, but I don't have to worry about it getting too hot and damaging the carpet or whatever surface it is on. UTHs can get much hotter than many people realize, they've been known to heat up to 120 degrees, and there is also a chance of them malfunctioning and getting even hotter than that. If you're going to use an UTH, I would highly suggest buying an inexpensive dimmer switch from walmart or any hardware store and plugging it into that so you can control the amount of heat produced. You would need an accurate thermometer to measure temps to know how much to adjust the dimmer also. I wouldn't recommended any type of bulb to provide heat because dubia can see even the light produced by even the "night" bulbs which could cause stress since the bulb would constantly be on, plus they're going to dry out the the bin much more quickly, lowering the humidity, which you definitely don't want. And while you do want a constant heat source, you might not need to supplement as much heat as you think, anywhere in the high 80's--low 90's is fine. They'll still breed at temps lower than this, just more slowly.
