Phylctic Parallelism in Metamorf>hic Species. 479 



flies such community is found in their diurnal habits, 

 and in accordance with this we find that these only, 

 and not their larvae, can be formed into a group 

 having common characters. 



In the larvae also we only find agreement in the 

 conditions of life within a much wider compass, 

 viz. within the whole order. Between the limits 

 of the order Lepidoptera the conditions of life in 

 the caterpillars are, as has just been shown, on the 

 whole very uniform, and the structure of the larvae 

 accordingly agrees almost exactly in all Lepidop- 

 terous families in every essential, i. e. typical, part. 



In this way is explained the hitherto incompre- 

 hensible phenomenon that the sub-ordinal group 

 Rkopalocera cannot be based on the larvae, but 

 that Lepidopterous caterpillars can as a whole be 

 associated into a higher group (order) ; they con- 

 stitute altogether families and an order, but not 

 the intermediate group of a sub-order. By this 

 means we at the same time reply to an objection 

 that may be raised, viz. that larval forms cannot be 

 formed into high systematic groups because of 

 their " low and undeveloped " organization. 



To this form of incongruence, viz. to the forma-, 

 tion of systematic groups of unequal value and 

 magnitude, I must attach the greatest weight with 

 respect to theoretical considerations. I maintain 

 that this, as I have already briefly indicated above, 

 is wholly incompatible with the admission of a 

 phyletic force. How is it conceivable that such a 



