ONTOGENY OF LARVAL COLOR PATTERNS. 151 



At ecdysis in this genus the color pattern or the dark elements thereof 

 develop around the centers of color and from there spread out to form larger 

 colored areas. In sequence the development is as follows : ( i ) Spiracula and 

 wing, (2) baso-tergal, (3) inner tergal, (4) middle tergal and inner sternal, 

 and (5) outer tergal and middle and outer sternal. The anterior members 

 appear earlier and are at all times more completely developed than are the 

 posterior members of the same homodynamous series. Exceptions to the 

 above are found only in some few species, in the larvae of which the sternal 

 centers develop before the tergal. These exceptions are of such small mo- 

 ment in larval coloration that they may be passed over as of no significance. 

 It is of interest to note that the order of the appearance of color centers at 

 ecdysis and of their development in the embryo are identical. In fact, 

 ecdysis, at regularly recurring periods reduces the color pattern of a larva to 

 an embryonic condition from which may arise the same color pattern or a new 

 one; but the new pattern is always developed around the same old centers. 



In the ontogeny of the coloration of the larvae each species studied passes 

 through a series of stages, beginning with one more or less simple or gener- 

 alized and ending with another of a more special character. Some species, as, 

 for example, undecimlineata and signaticollis, start with a very generalized 

 color pattern and pass rapidly through stages which end in a fairly specialized 

 condition. Other species, oblongata and dilecta, do not begin their larval 

 coloration with as generalized a pattern as does undecimlineata and others, 

 but with a pattern which corresponds very exactly to the second stage in the 

 development of the color in undecimlineata. In these instances have we an 

 example of Hyatt's principle of acceleration? And have we here also the 

 existence of localized stages in development corresponding to phyletic stages ? 

 These are questions whose discussion can best be postponed until after we 

 have examined the data of the ontogeny of imaginal coloration. 



The ecdysis at pupation removes all traces of larval cuticula colors, so that 

 such colors as exist during the pupal stage are developed therein. The pupal 

 stage, which is passed in the ground, is in most species characterized by 

 an absence of color, excepting the spots upon the abdominal tergae and 

 sternae, which in some species, as, for example, in signaticollis and oblongata, 

 are modified into black bands. These areas of markings, which can be of no 

 possible use to the animal, as it is completely hidden in the earth, represent 

 simply the revival of the color-producing power of the cells in the tergal 

 and sternal centers. All this pupal coloration, however, has no relation to 

 that of the imago, as it is cast away at emergence. The imaginal color 

 develops either under the pupal skin before emergence or in the hours imme- 

 diately following the final transformation. 



