by gradually increasing and decreasing the light intensity in the cage, and at 
the same time recording the variations with the actinometer that natural light 
behavior patterns can be compared to the on-off light patterns of a restricted 
laboratory situation. 
Figures 5 and 11 show a circuit that is used in a moth-activity and flight- 
behavior chamber designed by the author. It is a circuit adapted from the 
International Rectifier Corporation's Solar Cell and Photocell Handbook (Sasuga, 
1962) and is a transistorized relay switching circuit that utilizes an Al5 
selenium photovoltaic cell. The Photocell Handbook gives many simple transistor- 
ized circuits that can be easily wired, and would be useful to insect behaviorists 
in diverse experimental situations. 
The 50,000-ohm, washer-type, variable potentiometer (files 5) was constructed 
from pressure-sensitive paint; it is possible to set the operating threshold of 
the circuit by tightening the nut and bolt on the washer transducer. The 500,000- 
ohm rheostat is a positive feedback resistor that balances the circuit for sharp 
switching action and suppression of spurious oscillations. The photocell is 
shown hooked up for switch-on with illumination, but by simply reversing the 
photocell leads, switch-off may be accomplished with illumination. The circuit 
is excellent for moth activity recordings, as the circuit is sensitive down to 
1/2 foot-candle, which is well within the flight tolerances of almost all night- 
flying moths. Since the circuit is transistorized, it is small enough so that 
several can be mounted on the side of an activity chamber. The fast thyratron- 
like action of the circuit makes it valuable for counting and timing flights with 
an operational recorder. I have used it with a red filter over the light source 
to monitor a feeding station and take flight photographs of moths (fig. 12). Two 
or more cells may be mounted at either end of a flight chamber to count and time 
visits of moths to food or oviposition and sex-attractance sites, thus making an 
automatic olfactometer of the chamber. Since it is battery operated, it can be 
used to record moth visits to flowers in the field. 
The Amprobe recorder (fig. 9d) may be used as both a galvanometer-type 
recorder and operation recorder by mounting an inexpensive marking pen stylus relay 
above the pressure-sensitive paper. With this system, both varying light and 
time of flight can be recorded from the flight chamber on the same recorder. It 
is only necessary to hook a low-voltage, battery-operated relay across the 
contacts of the 1000-ohm control relay, and adjust the marking pen so that it 
strikes down, leaving a dot on the recorder paper. 
Figure 6 shows a simple circuit for recording pressure parameters by 
positioning a micro-ducer between the wings of a moth in fixed flight. A 
pressure-sensitive-paint micro-ducer is mounted over the back of the insect, and 
as the wings come together against the contact sides, a resistance change occurs 
in the circuit and is recorded in microamperes on the recorder. The author is 
still experimenting with this circuit. As Hefferline et al. (1960) point out, 
the mounting of such transducers is a difficult problem, and to eliminate error, 
they must be positioned so that the contactors (i.e., the wings) strike the 
circuit at the same position and angle. Further experimenting with pressure- 
sensitive paint may produce a reliable wing-pressure transducer. 
The pressure-sensitive paint is applied between two metal conducting 
surfaces, and may also be vacuum-coated to form a barometric pickup, or placed 
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