over a magnet with a soft iron contact on top to make a solid-state relay, 
amplifier, or wind- and water-pressure indicator. The manufacturer lists some 
of the following possibilities for imaginative experimenters: Measuring 
mechanical force, motion, pressure, altitude, vacuum, strain, shock, impact, 
acceleration, position, flow, vibration, weight, or thrust. It also has 
possibilities for uses in automation, such as in the development of a solid- 
state relay for use with counters, et cetera. The manufacturer makes several 
different types of paints from O to 1 p.s-i., up to 0 to 100,000 p-s.i. 
Transducers are also obtainable already mounted between disks or washers with 
the leads soldered in place. As pointed out above, I have used a washer-type 
transducer between a nut and bolt as a screwdriver- paisa potentiometer in 
the photocell circuit. 
There appears to be unlimited uses for such solid-state pressure mechanisms, 
and since they require no amplification in most cases, it may be possible to 
construct inexpensive apparatus for the study of moth aerodynamics. I once 
tested the holding ability of corn earworm moths on different surfaces (Callahan, 
1957) and the technique developed in that work might be improved by using such 
a pressure transducer as a strain gage to more accurately measure the clinging 
force of the moth on the surface. 
The examples listed above are but a few of the many possible uses of 
simplified semiconductor circuitry applicable to the study of insects. These 
circuits are only as reliable as their voltage source. For most uses a battery 
will suffice, providing it is constantly checked for stability and voltage. The 
1.4-volt, button-type, mercury battery is excellent as a voltage source for most 
of the circuits. An on-off switch should be included in all circuits, as con- 
tinuous discharge will soon cause erratic recordings and require recalibration 
of the circuit. Where long-period recording or continuous operation is desirable, 
a low-voltage, efficiently regulated d.c. rectifier power supply may be required. 
Many such stable rectifier circuits are given in the book, Metallic Rectifiers 
and Crystal Diodes, by Conti (1958). 
Read-out of circuits may be direct in microamperes, or it may be preferable, 
as in the case of light, to convert microamperes to langley or foot-candle units. 
Such calibrations may be made against a standard pyrheliometer or foot-candle 
light meter (Callahan, 1964) and the calibration curve kept with the recorder. 
For a list of conversion factors from unit to unit, the reader is referred 9 
the booklet, Conversion Factors, published by the Sillcocks-Miller Company .2 
Photometric units are completely defined in chapter 1 of the International 
Rectifier Corporation's Solar Cell and Photocell Handbook. 
It is hoped that this summary of semiconductor circuitry and its usages in 
insect ecology and behavior will induce more entomologists to use the fine 
electronic tools now available to biological scientists in conducting their 
research. 
