Abstract
The alpine grasshopper Kosciuscola tristis shows a physiological colour
change under the control of temperature. Males are a bright greenish blue
above about 25�C and a dull near-black below about 15�C. Intermediate
shades are developed at intermediate temperatures. A similar, but less marked,
change occurs in the female. The colour change in the male was studied with
the aid of a special colour chart, which enabled quantitative ratings of colour
to be made.
The histology of the integument is described. In the pale phase a dense
layer of highly refractive, very small granules occupies the distal portion of
the cells of the epidermis; these are underlain by a layer of larger dark brown
granules. In the dark phase the position of these layers is reversed and the
nuclei are raised above the basement membrane, on which they rest in the
pale phase. At intermediate colour shades the granules show transitional distributions.
It is concluded that the colour change is brought about by the
migration of the two types of granule in opposite directions within the
epidermal cells.
The ecology of K. tristis in its natural habitat is discussed. On clear days
the insects become pale 2-3 hr after sunrise and begin to turn dark again during
the late afternoon; the night is spent in the dark phase. The colour follows
closely the temperature given by blackened thermometers, but at any given
temperature it differs from the equilibrium colour developed when that temperature
is maintained constant, because of the lag in accommodation to the
continuously changing temperature in the field. It is suggested that the colour
change may have a thermoregulatory function.
Two undescribed species of Kosciuscola show similar colour changes, but
these are confined to the face and ventral surface. The same two types of
granule are present in the epidermal cells, including those of the dorsal surface,
where they are distributed as in the pale phase of K. tristis at all temperatures.
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics
Cited by
56 articles.
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