In entomological investigations it is frequently desirable to use varying temperatures rather than constant temperatures. The apparatus herein described, when installed in a rearing or storage chamber, makes it possible to control temperatures in any desired graph pattern over a period of twenty-four hours, and to repeat the same pattern any desired number of times. This is accomplished by removing the usual adjusting mechanism from a DeKhotinsky-thermo-regulator and substituting for it an automatic adjuster operated by a synchronous electric clock.