48 ILLINOIS BIOLOGICAL MONOGRAPHS [442 



this normally brown species resembles the green form of the Atlantic 

 coast (Fig. 553), differing only in lacking bluish reflection. From 3 

 to 15 days yellow reflections are at their maximum. Specimens occas- 

 ionally are collected in this stage (September). After this the color 

 begins to shift to red or dull brownish red, but has still greenish reflect- 

 ions in some individuals which gradually disappear with hibernation. 

 The reddish reflections loose luster and turn to a dull brown by the time 

 the adult dies in the latter part of June after reproducing (Fig. 551). 

 Important differences occur between individuals collected at different 

 times of year. 



Figures 559 to 562, plate XXX, show the development of the color 

 in C. hirticollis. Here again the color begins as green and gradually 

 shifts to brown or reddish brown. There are no green varieties of this 

 species but it often shows greenish reflections in the adult condition. 

 This is more pronounced in fresh individuals. 



Figures 563 to 565 show the development of the color in C. pur- 

 purea; the first stage shown (Fig. 563) compares favorably with some 

 forms of the variety graminea. As time goes on the color shifts to red 

 over the upper surface of the elytron and the blue margin shifts to 

 green, both shifts being down the spectrum. Black specimens occur 

 with this species in the locality where the larval stages were collected 

 for these observations. 



C. purpurea limbalis shows a similar series of stages, and the shift- 

 ings which are similar to those in the form purpurea-graminea-auduboni 

 shown above. In general during ontogeny in the species noted the color 

 shifts down the spectrum as the cuticula hardens and pigment appears. 

 In fact from blue to green the change is direct; but in passing from 

 green to red the orange and yellow are not noticeable or at most occur 

 as slight reflections ; green changes to reddish green, red, and 

 finally a dingy brown almost black in a few individuals collected in 

 August and September with the new generation. A series of individ- 

 uals killed, pinned, and dried so as to show a series from the beginning 

 of color development to completion, is remarkable in that the earliest 

 stage when dried is dull black, the second purple, the third blue, and 

 individuals in the green stage (Fig. 573, PI. XXXI) usually turn 

 fiery red on drying (Fig. 576, PI. XXXI). Heylaerts (1870) performed 

 experiments on color changes in some European species. Brown speci- 

 mens of C. hybrida when heated to 102° C. turn green and remain so 

 for a short time when exposed to the atmosphere. The change to brown 

 is hastened by blowing the breath on them. They remain green in a 

 sulphuric acid desiccator. Green C. campestris turn blue when simi- 

 larly treated. These changes accompany the almost complete removal 



