1969] 
Willey and Willey — Social Displays 
295 
Finally, there is the silent raising and lowering of the legs by both 
sexes, nymphs and adults ? which seems related to what Otte (1968) 
calls “femur-raising”. The femora are raised relatively slowly to 
the vertical position and the tibiae are extended during this time 
about 30° to 60 0 from the closed position. The complete motion 
takes about one second and may take longer. This motion; is fairly 
constant in detail and is a warning signal to any insect approaching. 
In nature, the intruder usually avoids the femur-raising insect or 
begins a definite social reaction. The effect of the signal, then, is 
to advertize that the grasshopper is not an inanimate object suitable 
for tasting or crawling upon. First instar nymphs exhibit this 
behavior as soon as they emerge from the pronymph. In captive 
populations this motion intergrades with the intense repulsion dis- 
play of non-receptive adult females mentioned under courtship. 
Under crowded conditions, even males may begin tibial-waving and 
other signs of intense disturbance, but usually the warning signal 
does not vary much in normal interactions. 
Extraneous sounds and the use of models. 
Males will respond to motions other than the normal interaction 
noises. The human voice commonly is ignored by grasshoppers, but 
broad spectrum clicks and other sounds with sharp wave fronts pro- 
duce definite effects in the behavior. These effects range from sudden 
freezing in position to flight, to assumption of the alert pose or even 
orientation toward the source. A chipmunk ( Eutamias sp.) called 
25 feet away while one of us was watching two males interact; they 
oriented to the source and ran about 12 inches toward it. Although 
they did not chirp, the sudden and simultaneous nature of their 
activity with the final pause in full alert pose, was characteristic of 
presocial orientation behavior. Figure 5 shows the vague resemblance 
of the chipmunk’s alarm cry to the chirp of the courting male. The 
aforementioned Exakta reset buzz (Fig. 3) is another example of 
the ease of producing social behavior with artificial acoustic models 
and indicates that the acoustic and visual signals produced by the 
same motion are not necessarily closely linked, but rather only 
intensify the effect. 
Males will also mount and attempt to copulate with sticks, ther- 
mometers and the rolled edges of cardboard cream cartons. However, 
approach sounds are seldom used to communicate with motionless 
objects. They seem to come upon these items by accident and 
proceed with the use of tactile feedback. This behavior seems to be 
characteristic of males between 15 and 25 days old. We are presently 
