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ISCIENCK 



[N. S. Vol. XI. No. 266. 



pattern but are yellow or orange in color. 

 Yellow and orange are hypodermic colors 

 according to Hagen. These beetles are few 

 in number. I have not yet been able to get 

 material to study one of these forms. 



In all the beetles that I have studied 

 color appears first over the origin or at- 

 tachment of the body muscles to the cu- 

 ticula. No color appears upon the wings 

 until they are out of the pupa case and the 

 wings are fully expanded. Then color ap- 

 pears first between the nervules as longi- 

 tudinal bands which may become confluent, 

 remain as bands or break up into rows of 



The pupa becomes first white (i. e., a 

 yellowish white), then yellow or ochre 

 yellow, then the special adult colors develop 

 so that the sequence of development is yel- 

 lowish white (due to the color of htemo- 

 lymph), yellow, ochre yellow, yellow brown, 

 brown, dark brown and black. 



II. The pigment forms, first as a waxj' 

 transparent layer upon the surface of the 

 cuticula. This waxy layer is excreted 

 from hypodermal gland cells having open- 

 ings upon the surface. This waxy secre- 

 tion forms a secondary cuticula which is 

 the pigmental cuticula ; the primary (em- 

 bryonic) cuticula is unpigmented. 



After the waxy laj'er has attained a con- 

 siderable thickness, it becomes darkened 

 over the places where dark pigment is to 

 develop. This layer is homogeneous with- 

 out lamellae or pore canals. Only dark, 

 i. e. , black brown or dark red color appears 

 to be formed in this secondary cuticula 

 layer. Yellow is always formed from the 

 precipitation of solids from the hsemolymph 

 in or among the hypodermal cells. 



If the hfemolymph is allowed to dry in 

 the air, it becomes yellow brown in color, 

 and when some quantity is allowed to dry 

 it appears very dark or even black by re- 

 flected light. If hsemolymph is precipita- 

 ted by heat, a yellow mass is thrown down, 



leaving an ochre yellow fluid, which can be 

 decanted off. The yellow precipitate in 

 sealed tubes bleaches on exposure to light. 

 It also darkens on exposure to air. If 0, 

 be passed through the yellow liquid, it 

 rapidly becomes dark brown, and on con- 

 centration by evaporation, leaves a waxy 

 residue. 



If the hsemolymph be mixed with .1% 

 HClHCjHjO, or almost any acid, it becomes 

 red, but the yellow color is restored by an 

 alkali as .5% NHpH. 



III. I have been unable to determine 

 the composition of the pigment, owing to 

 the difiiculty of isolating it. I have made 

 some tests upon the hsemolymph and have 

 demonstrated Fe, N"a, Mg salts, albumen, 

 fibrin, globulin, xanthophyl to be present. 



IV. Summary of results : 



(a) On the body color (dark) develops 

 first over the attachment of the muscles to 

 the cuticula. 



(6) The multicolorous type of color pat- 

 tern is the least specialized ; the unicolor- 

 ous type having dark color is the most 

 specialized, and the unicolorous yellow type 

 is the most primitive of color pattern in 

 Coleoptera. 



(c) The pigment is situated in a second- 

 ary cuticular layer external to the primary 

 cuticula which is unpigmented. 



(d) The pigment is derived from the 

 hsemolymph of the pupa. The dark pig- 

 ments, black, brown and some reds are de- 

 rived from the oxidation of a substance, 

 elaborated from the more liquid part of the 

 hsemolymph by the hypodermal gland cells. 

 Yellow is due to the precipitation of the 

 solid parts of the hsemolymph among the 

 hjrpodermal cells. 



(e) Yellow and red are the neutral or 

 alkaline, and the acid modification of the 

 same substance. This substance I believe 

 to be like litmus in its reaction to acid and 

 alkali. 



Yellow is the more primitive color, while 



