Conversion Equipment to Produce a Cyclic Environment within Constant Temperature Cabinets

Abstract

The effect of environmental variation upon insect behavior has been evaluated in the past by utilizing specially designed cyclic temperature cabinets. These cabinets are programmed to produce daily fluctuations in temperature which simulate specified climatic occurrences common to the apparent geographical range of the insect in question. These environmental manipulations make possible the continuous, close observation of study material within the laboratory and consequent discovery of biological phenomena that might be easily overlooked in the field. For example, simulated daily cycles demonstrated a good correlation between environmental conditions and the number of progeny produced by the oriental fruit fly, Dacus dorsalis Hendel, (Flitters and Messenger 1953). In other cases, cyclic cabinets may be used to control photoperiods as well as femperature and humidity oscillations during diapause studies of insects exhibiting multi-voltine life cycles. Basically the production or reproduction of a particular climatic environment for studies of terrestrial insects involves controlled oscillations of temperature, light, and humidity. A suitable cabinet should produce a wide range of combinations of these three variables, retain a relatively simple electronic design, and be inexpensive to build. The control system for each variable should work independently from control systems for other variables, thus enabling the production of any set of environmental conditions. Numerous cabinets have been developed with a control system for a single environmental factor and a few commercially available cabinets control temperature, humidity, and light simultaneously. Designs for the production of daily cycles of temperature have been incorporated into household refrigerators equipped with heating elements and air circulation systems (White and DeBach 1960), into constant temperature cabinets (essentially the same as the household refrigerator design), and into walk-in coolers (Flitters and Messenger 1953). The control systems involve a mechanical or electronic device that provides continuous adjustment of a thermoregulator throughout the period of operation. These devices are basically of the same design: a one-revolutionper-day or week motor controls the daily cycle. Connected to this motor is either a cam (for irregular cycles), a variable length lever (for relatively homogeneous cycles), or an electronic plate (temperature cycles are controlled by a printed circuit of any design). From these discs, the temperature program is transmitted either by mechanical or electrical followarms to the thermoregulator. Each system has its advantages and disadvantages. The printed circuit board design of Munger (1944) is expensive from the standpoint of