Temperature-Constant and Temperature Gradient-Free Insectary: Design and Operation

The Metabolism and Radiation Research Laboratory is involved in a research program that concerns the environmental control of diapause in insects. We therefore needed a facility in which we could arrange tiers of experimental chambers that would not be exposed to significant variations in temperature in time or space, because temperatures must be controlled to ±1°C if we are to obtain reproducible biological data. For example, in some expensive commercially available environmental chambers, both vertical and horizontal temperature gradients exist. If such chambers were used for studies of photoperiodism, the replicates would have to be tested at the same coordinates of space. In other words, I replicate could not be near the floor of the chamber and 1 near the ceiling. Also, the rearing of insects on artificial diets requires close control of temperature. For example, when larvae of the boll weevil, Anthonomus grandis Boheman, are reared in petri dishes, the diet loses moisture which condenses on the lid if the temperature drops; then these water droplets fall onto the diet and allow mold to grow.