ACRIDIIDiE. 
75 
to changes of season. Young grasshoppers hatching in the rains are 
frequently green to harmonize with the growing vegetation; this often 
gives place to 4 ‘dry grass colour’ 5 in the adult which is found in October. 
Others which live on dry soil, on rocks, on moors, on sand dunes are 
coloured in shades of grey and brown with lighter markings and spots; 
in nearly all the colours are dull, and though varied, evidently cryptic. 
In the true locusts further and more striking colour changes take place, 
one of which is the “swarming colour,” a vivid red, that probably facili¬ 
tates migration by rendering the swarm visible at a distance and enabl¬ 
ing all to join it. A very few are vividly coloured and undoubtedly exhibit 
warning colouring; this is correlated with the habit of living exposed 
on the plant and the young are also warningly coloured, though not 
always in the same 
tints as the adult. 
In a large number of 
cryptically coloured 
forms, we find that the 
lower wings are bright¬ 
ly coloured; in flight 
this colour is very con¬ 
spicuous and it is not 
difficult to follow the 
j erky zigzag flight with 
the eye; but as the 
wings close on the 
insect settling, all trace 
of the colour is lost, 
the tints of the upper 
wings and body blend 
with the surroundings, 
the insect sits still and 
vanishes before one’s 
eyes. There is no 
doubt that the bright 
Fig. 20—Tylotropidius didymus. colours of the lower 
wings, which sometimes extend to the sides of the abdomen, are 
“deceptive” and materially assist in the escape of the grasshopper 
