158 COLORATION IN LEPTINOTARSA. 



pale yellow-white hypodermal color, with the initial appearance of cuticula 

 color on the anterior segments in the inner and outer sternal centers, although 

 the middle sternal center lags somewhat behind the others (figs. 2 and 7). A 

 difference between the two species may now be easily seen. In L. undecim- 

 lineata color spreads from the centers peripherally (fig. 8) until very soon 

 dark bands are found completely across the anterior half of the segment, and 

 these later extend caudalward and over the entire segment. In oblongata, 

 however, color does not extend beyond the centers to any great extent, the 

 modifications being limited to the fusions of centers shown in figs. 2 to 5. As 

 far as changes in the cuticula color are concerned both species pass through 

 essentially the same stages. 



The pleural and tergal portions of the segments show exactly the same 

 phenomena of color development as those found on the sterna?. These are 

 represented in side view in these two species in figs. 1 1 to 20. Upon all parts 

 of the abdominal segments the centers of coloration found in the correspond- 

 ing segments of the larvae are preserved ; and although in the adult these cen- 

 ters may fuse to form a unicolorous surface, the fact that in ontogeny it is in 

 these centers that color first appears indicates that they are of great persist- 

 ence as color units. 



On the last two thoracic segments also the color development is almost 

 exactly a duplicate of that found upon the abdominal segments. The homo- 

 dynamous centers of coloration are clearly distinguishable and present in all 

 respects the same conditions as those found upon the abdomen. 



GENERAL ASPECTS OF COLOR AND COLOR-PATTERN ONTOGENY. 



Studies upon the ontogeny of the color pattern on the body of insects are 

 few, those of Kunckel de Herculais, of Enteman, and of myself being all that 

 are extant, excepting a few fragmentary observations. All the observations 

 that have been made along this line are, however, in accordance with the laws 

 which I have found to apply in general to insects. 



The general color development over the entire body in Leptinotarsa does 

 not differ in any respect from that which I have described for many other 

 genera of Coleoptera and other groups of insects, nor from that described by 

 Enteman for Polistes. Color is seen first on the head in the pigment cells of 

 the eye ; and this appearance of pigment in the eye is the best indication that 

 the color pattern is about to develop. Of the color pattern proper traces are 

 found first upon the mouth parts and upon the epicranium in the paired cen- 

 ters already described; soon thereafter it appears upon the pronotum and 

 upon the sternal elements of the thoracic and abdominal segments. Upon the 

 dorsal side in most species the color lags behind, and on the wings in all spe- 

 cies its appearance is postponed until after emergence, while the full adult 

 color is not attained on any part until some time after emergence from the 



