Insect Life. 233 



distinguishing between species and varieties ; that 

 geographical races are local forms completely fixed 

 and isolated ; that representative species are better 

 distinguished from each other than local forms and 

 sub-species ; that the species of large genera vary 

 more frequently than those of small genera, and 

 that specific differences in the former are often ex- 

 ceedingly small ; that fecundity does not determine 

 the rate of increase ; that the struggle for life is 

 most severe between species of the same genus ; 

 that secondary sexual characters are generally dis- 

 played in the same parts of the organisation in 

 which the species of the same genus differ from 

 each other ; that distinct species present analogous 

 variations ; that similar structures are often inde- 

 pendently developed ; the varying importance for 

 classification of the same important organ in the 

 same group of beings ; that analogical or adaptive 

 resemblances are misleading for classification ; that 

 the great frequency of mimicry among insects is 

 associated with their small size and general defence- 

 lessness, as no species furnished with a sting, or 

 other defensive property, is known to mimic other 

 species ; the importance of relative position or 

 connection in homologous parts ; the remarkable 

 changes of structure effected during development ; 

 that adaptation to the conditions of life in the in- 

 sect larva is just as perfect and beautiful as in the 

 adult animal, and that, consequently, lar\'ae of dif- 

 ferent orders are often similar, and larvae belonging 

 to the same order often very dissimilar ; that larval 

 and pupal stages are acquired through adaptation. 



