DAY-FLYING MOTHS. 187 



the different groups, until we perceive an almost con- 

 tinuous chain. An observation of Kirby and Spence on 

 this point : "It appears to be the opinion of most modern 

 physiologists that the series of affinities in nature is a 

 concatenation or continuous series ; and that though an 

 hiatus is here and there observable, this has been caused 

 either by the annihilation of some original group or 

 species ... or that the objects required to fill it up are 

 still in existence but have not yet been discovered." 

 Later-day naturalists find in these intermediate grada- 

 tions, or transition states, such as I have indicated, and 

 others, their stronQ^est arsiJfument for the Darwinian 

 doctrine of community of descent. 



The Abnormal Collection of Pretty Insects Cast nil dee. 



Let us glance at the curious and abnormal collection of 

 pretty insects, Castniidse, which, in some respects, com- 

 bines the characters of both Lepidopterous divisions, but 

 in modern opinion has most affinities with the moths (see 

 Fig. 36). Linnaeus, and all the writers of the last century, 

 regarded the species of the genus with which they were 

 acquainted as butterflies, including them in the great 

 group Papilio, on account of the clubbed structure of their 

 antennae. At the beginning of the present century, 

 when this group was broken up, the genus Castnia was 



