THE HAWK MOTHS (SPHINGIDAE). 227 



spines are gradually lost as the caudal horn became 

 variously formed. The Sphingidae have become smooth, 

 and show only a thoracic crest or the anal spine re- 

 presented by a horn. Probably the Sphingidae were 

 cast off from the Bombyces or Spinners parallel with 

 the Ceratocampinae. That the Sphingidae may have 

 been evolved from the ancestors of the Ceratocampinae 

 we have reason to believe. The sub- family Smerin- 

 thinae would seem to be descendants of the oldest forms 

 of the Sphingidae. The small and sunken head, the 

 shape of the thorax, and the pectinate antennae are 

 probably low characters in the Hawk Moths, and recall 

 the Bombyces ; as also the subterranean pupation 

 without silk, together with the nocturnal flight. The 

 mode of flight of the Smerinthinae, which is opposed to 

 the characteristic manner of other hawk moths, and 

 their rudimentary mouth-parts, which prevent them 

 feeding in the perfect state, likewise show affinity to the 

 Bombyces. It is therefore manifest that these two 

 marked features of the hawk moths that they feed 

 freely and are highly specialized in relation to flowers 

 were wanting in their Bombyciform ancestors, and are 

 still wanting in Smerinthus. 



When we turn to the general distribution of these 

 moths, we find that while the Old World possesses a 

 somewhat fuller and better representation of the higher 

 groups, in America the grey, moth-like Sphinginae exist 



