130 COI^ORATION IN I^PTINOTARSA. 



cies are produced by cuticula pigments, are permanent, and are with difficulty 

 soluble in the same reagents as the darker colors. 



Between the browns and yellows transitions in the adult or in the larvae are 

 few, but in the ontogeny of the animal they are common, as in the develop- 

 ment of the black or brown areas of the species mentioned. The yellow, 

 as in L. decemlineata and its allies, is only slightly developed and is of no 

 great permanence, fading on exposure to light, with age, or on treatment with 

 reagents. It is in these beetles the least permanent of the cuticula colors, and 

 is in fact of relatively little importance in the production of color patterns.^ 



The dark markings — that is, the black or brown spots — of the larvae and 

 pupae of this genus are also cuticula pigments like those discussed above. 

 These are the pigments described by Poulton in lepidopterous larvae as 

 "proper to the species." 



When studied in sections of sJ-f^-to 6| [j- thickness, these pigments are 

 always seen to be diffuse and not in the form of granules, as claimed by 

 Hagen, and recently by Enteman in Polistes. They are limited entirely to 

 the primary cuticula, and the transitions from pigmented to unpigmented 

 areas is rapid but continuous. 



Always closely associated with the cuticula pigments in the production of 

 color patterns in these beetles are the hypodermal pigments, which, as far as 

 I know, are always yellows and reds in this genus. These two colors exist in 

 the form of small granules in the hypodermal cells, and, although more or 

 less permanent, they all fade at death or on exposure to light, and are easily 

 soluble in water, alcohol, and other organic solvents. The chrome yellow so 

 often seen in decemlineata when freshly emerged is due to these pigments; 

 but undecimlineata never possesses them and is, therefore, of a white color 

 with black markings. In decemlineata, however, the yellow color fades 

 rapidly on exposure to light or with age, so that old specimens have the light 

 areas between the black stripes nearly white. The white is opaque, however, 

 and not translucent, as in undecimlineata. When freshly emerged from the 

 pupa decemlineata has a distinct reddish color, which gives away to chrome 

 yellow before the animal leaves the pupal cell, and later in life becomes white. 

 In rubicunda, however, the red color is retained and grows more intense. It 

 is not lost on exposure to light or with age, but fades to a dull yellowish white 

 at death. In rubiginosa in life the color is deep red, but at death changes to 

 a dull brick-red or yellow. 



These same yellows and reds are also found in the larvae of the species 

 described, and, as far as surface observations can determine, are continued 

 over from larva to pupa and imago. They are difficult to investigate in 

 sections because the ordinary reagents of microscopic technic dissolve them 

 completely long before the tissue is ready for study. By freezing, good 



* These cuticula yellows must not be confused with the yellow colors often produced 

 in the cuticula at death. These latter colors are due to post-mortem changes and to 

 drying of the integument. 



