459] COLORS OF TIGER BEETLES—SHELFORD 65 



characters is found iu many patterns illustrated in the plates, particu- 

 larly plate XXXVIII. The series of three species thus show the same 

 tendency, with respect to the middle band. This must be due to the 

 existence of the same mechanism for heredity and response. The next 

 step to important discovery probably lies in the direction of further 

 analysis of the mechanism by experimental means, which may include 

 surgical and mechanical experiments on the developing wing covers, 

 and analysis by such methods are commonly used by the breeder. 



BEARIXG OF THE PATTERN MECHANISM ON THE BIOGENETIC LAW 



The data accumulated in connection with this study shows certain 

 principles'''coficerned with the application of the biogenic law. First 

 the general plan of the pattern seems to be common to all insects. The 

 ancestry of the insect group is too obscure to justify the assumption 

 that any original ancestor possessed a wing with nineteen spots such 

 as arei shown in the elytron of Cicindela, or that such an ancestor 

 possessed longitudinal stripes or cross bands. The evidence seems to 

 indicate that the tiger beetle group sliows a type of pattern mechan- 

 ism described at length in the preceding pages; that this pattern 

 mechanism is plastic at least in the more generalized species; that 

 from this plastic mechanism certain definite lines of modification have 

 been somewhat fixed and limited. So long as the ontogeujie features 

 are concerned with the general mechanism one is not justified in calling 

 the appearance of certain spots recapitulations. They may full.v as 

 well be areas which are less favorably nourished or which are made up 

 of cells with lower rates of metabolism (see p. 31). Either of these 

 physiological conditions may be due to mechanical necessities in devel- 

 opment in all insects primitive and specialized, and if so, why call them 

 recapitulations 1 



Such evidences of recapitulation as do occur are found in the re- 

 currence of markings in development which represent those occurring 

 in related species or varieties. Thus, as I have noted, a curved middle 

 band occurs in the ontogeny of some specimens of C. Iccontri and du- 

 plicates a late stage in the loss of this marking as sho^ni in figure 115, 

 plate IX. Here a curved and degenerate form of this marking occurs 

 temporarily during ontogeny and may perhaps be regarded as recapitu- 

 lation. The application of the biogentic law must generally be fol- 

 lowed with great caution in dealing with insect patterns and no doubt 

 with many other phenomena. 



