STUDIES ON PERILLUS BIOCULATUS FAB. 890 
In the male sex, then, the only way of raising the physiological activity 
to a point where white color forms appear, is by rearing the bugs 
under high temperatures. 
In Conclusion 
It appears to the writer that Perillus bioculatus is, even among the 
Hemiptera, an exceptionally good form for the study of color in an 
insect. Bearing in mind that the food of this species is nothing but 
the body fluids of the potato beetle or its immature stages, and the 
quantity all that the bug desires, certain food factors that might influ- 
ence changes in color are here reduced to a minimum. 
Experiments show that low temperatures cause a greater deposit 
of coloring matter in the hypodermal layer, and with this condition 
a lower rate of physiological activity can be correlated, namely, longer 
periods of growth for nymphs to reach the adult stage. Apparently 
it is not temperature directly that affects the deposit of coloring matter 
in the hypodermal cells, but the influence of temperature on the phy- 
siological processes of the insect. With the ceasing of physiological 
activity, as in hibernation, no changes in color can be observed. 
Since a maximum amount of pigment is deposited in the body wall 
under low temperatures (65°-75°F.), and the minimum amount de- 
posited under high temperatures (85°-95°F.), it appears that increased 
metabolism does not produce pigment, but on the contrary must con- 
sume or otherwise dispose of the materials which under lower tempera- 
tures are laid down as pigment in the body wall. In this connection 
it is interesting to note that the most frequently found yellow and red 
pigments, in both plants and animals, belong to the group known as 
Carotinoids (Palmer, 1922). Furthermore, it has been shown by 
several workers that the carotinoid pigments oxidize readily in animals 
having a high rate of metabolism. Palmer (1922, p. 136) states: “The 
normal cause of the disappearance of carotinoids from both plants and 
animals is an oxidation. This is undoubtedly their ultimate fate in 
animals unless they are secreted in the milk fat or egg yo!k (in fowls) 
or stored up as adipose tissue and thus protected from oxidation. 
Where the oxidative tone of the body is low, as in diabetes, coupled 
in many cases with abnormally large intake of carotinoids, it is not 
surprising that the pigments should appear in the tissues in abnormally 
large amounts. ‘This is especially likely to be true of the epidermal 
tissues inasmuch as the effect of eating carotinoid-rich diets in normal 
persons shows that the subcutaneous glands can serve as an excretory 
medium for these pigments.” 
