


Energy, Arbitrary Units 

/1TTL 
ES] 
6 
Wavelength ( Microns) 





Figure 2,--Increase in mean wavelength of radiation as temperature is reduced (after Summer 1962), 
longer sensitizing our eye (fig. 2). Inability 
of our eye to detect black heat does not mean 
that such a_ self-emitting body is not in- 
candescent. 
As Barnes (1963) pointed out, such objects 
emit no visible light and thus must be illumi- 
nated by some external hotter source to be 
detected by the eye. However, to any instru- 
ment having IR detection capabilities, these 
objects would be highly incandescent. All 
objects in nature, regardless of their tem- 
perature, are IR incandescent. Animals and 
plants are constantly absorbing and emitting 
IR radiation. In short, nature is inherently a 
thermal IR environment, and all objects in 
nature with high emissivity (table 1) are in- 
candescent point sources of IR radiation. 
BIOLOGICAL DETECTORS 
If we are to assume that insects, and in 
particular moths, can detect IR, then we must 
examine closely their anatomy to determine 
whether they have any organs that might be 
considered as having an IR detector con- 
figuration, 
The most obvious areas of interest for 
study are the compound eyes and the ocelli, 
both of which have optical configurations. 
Modern microwave techniques, however, in- 
dicate that the antennae also display certain 
characteristics that should be subjected to 
considerable investigation. Smith et al. (1957) 
noted that by using microwave techniques we 
may now observe heat radiations. Blackbodies 
in the form of lossy waveguide terminations 
are used to calibrate receivers in the 8-mm. 
wave band. We shall examine the antennae 
first. 
Most moth antennae are very stable in free 
flight (Callahan 1965a), and are located for- 
ward and away from the body of the flying 
moths. Thus, the antennae sensilla, displayed 
against the nighttime background, are rela- 
tively free of any interference from the thermal 
emission of the moth's body. 
In the microwave region of radio there are 
three tuneable frequency configurations called 

