COMBINATION COLORS. I3I 



sections have been obtained which show the location and character of these 

 pigments. 



The relation between the cnticula and hypodermal colors in the production 

 of color patterns in these beetles is this : The hvpodermal color plays the part 

 of a ground upon which the darker browns and black stand out as spots and 

 stripes ; or, if the cnticula colors are extensively developed, the hypodermal 

 colors show through holes and rifts in the cuticula color as lighter spots. 

 Only rarely does one class prevail to the exclusion of the other. In rubigi- 

 nosa the prevailing color is hypodermal, red, the dermal being confined to the 

 appendages, whereas in modcsta no hypodermal color is visible, and in punc- 

 ticollis only a few small, yellowish spots are found. 



The subhypodermal pigments play no part in the adult coloration of these 

 beetles ; for, although they are present in the larva, pupa, and imago, it is only 

 in the larvae of a few species that they are visible. When found the color is 

 always a yellow or a reddish yellow, due to a modified, derived pigment, and 

 it helps to intensify the yellow or red of the hypodertnis. Sometimes, as in 

 decemlineata, a change of food will change the nature of this derived pig- 

 ment, and thereby the ground color of the larva. In this form larval color 

 ranges from deep red to a pale yellowish red, due solely to variation in the 

 subhypodermal pigment contained in the larval haemolymph. In a few spe- 

 cies, undecimlineata and diversa, the haemolymph and fat body are unicolored, 

 so that the larvae have a white or a translucent appearance, depending upon 

 their stage of development. These larvae are translucent in early stages, but 

 later on the development of the fat body gives them first a chalky white and 

 then a pale creamy white ground color. 



PHYSICAL OR STRUCTURAL COLORS. 



Pure physical colors are absent in this genus, excepting white, which is 

 produced by the fat body in larvae {undecimlineata) or by reflection from 

 crystals or other surfaces in the integument. This is of no importance in the 

 coloration of the genus. 



CHEMICO-PHYSICAL OR COMBINATION COLORS. 



In the larvae and pupae of Leptinotarsa these colors are wanting, but in the 

 imago they, in connection with the cuticula colors, are productive of interest- 

 ing changes. These changes consist in the forming of metallic colors, green, 

 blue, violet, and combinations of these with black, green, greenish black, 

 blue-black, etc., colors very common in this genus. These colors are all due 

 to thin lamellae over dark absorptive pigment. Scales and striae are wanting, 

 and pits are not developed sufficiently to produce physical color changes. 

 The effect of these chemico-physical colors in this genus is to transform to a 

 metallic color areas that would otherwise be a dull black, and thus in a sim- 

 ple but effective manner to produce differences, often of specific value. 



