July 1964 ARS - 33-94 
United States Department of Agriculture 
Agricultural Research Service 
BASIC SEMICONDUCTOR CIRCUITRY FOR ECOLOGICAL AND 

BEHAVIORAL STUDIES OF INSECTS 
by Philip S. Callahan 
Entomology Research Division 
I have prepared this report primarily to answer queries entomologists 
about electronic techniques I have used in my ecological studies of the corn 
earworm, Heliothis zea (Boddie). In these studies, conducted for the most part 
at the Southern Grain Insects Research Laboratory at Tifton, Ga., during 1962- 
63, I utilized certain standard circuits, which I modified slightly. These 
original circuit designs can be found in the publications on electronics marked 
with an asterisk in the References Cited section on page 9 of this report. 
This report includes descriptions of basic semiconductor circuitry for 
accurate measurements of an insect's environment and behavior; some methods for 
using Ohm's law to calculate resistance in meter-recording circuits; an expla- 
nation of the characteristics of photoconductive and photovoltaic cells, 
thermistors, and pressure-sensitive microducers; and a presentation of schematics 
and examples of many simplified semiconductor circuits I have used to study the 
environment and behavior of the corn earworm moth. 
From the first discovery by Edmond Becquerel in 1839 of the photoemissive 
effect, until after 1930 when the theoretical studies by Hertz, Elster, Geitel, 
et al. had been accomplished, little practical use was made of the unusual 
solid-state phenomena, most probably because of the small amount of electrical 
current they generate or control. In the years since World War II, however, the 
development of solid-state physics has progressed so rapidly, and semiconductors 
are now employed in such a diversity of circuits, that it is almost impossible 
to remain abreast of the field. New uses for control and recording mechanisms 
are limited only by a person's imagination, and entomologists, once they become 
acquainted with the subject, are apt to increase the list of uses indefinitely. 
Recording 
The circuits described here are for read-out on a microammeter or a micro- 
ammeter-galvanometer recorder such as ,the small, inexpensive, 50- or 100-micro- 
ampere Amprobe “ recorder (fig. 9d) yy There are over 200 manufacturers of 
ay Mention of a proprietary product in this publication does not consti- 
tute a guarantee or warranty of the product by the U.S. Department of Agricul- 
ture, and does not imply its approval by the Department to the exclusion of 
other products that may also be suitable. 
