NATURAL SCIENCES OF PHILADELPHIA. 31, 



and Bombycidse of X. A." Having taken a number of larvae of 

 Arachnis picta, Packard, on the 9th of May, 1870, near San 

 Francisco, he placed them in a box, and furnished them with a 

 plentiful supply of their appropriate food for two weeks. They 

 declined to eat, however, and remained thus for a period ex- 

 ceeding three months, when they passed into chrysalides, a few 

 without spinning cocoons. The remainder, as though all the 

 moisture in the body had been eliminated during their protracted 

 fast, wove a very thin open wdiite web, dotted with minute glisten- 

 ing beads like tin}' dew-drops. Here there can be no doubt as to 

 the part which lack of nutrition has played. If these examples of 

 almost complete starvation had appeared late in the season, the 

 effects would have been attributed in a measure to climatic influ- 

 ence ; but, in the language of Mr. Stretch, they were brought 

 about " in the height of summer." 



Some few of the Bombycidse are not cocoon-builders, but merely 

 pass into chrysalides. On the principle that these are the modi- 

 fied descendants of pre-existent forms that possessed the habit, 

 we are prepared to explain very much of the mysteiy which 

 envelops Acronycta and Arachnis. This acquired habit upon 

 the part of each, if permitted to bear offspring, would no doubt 

 react favorably in the line of higher development. At this point 

 a few hints upon the present natural arrangement of lepidopterous 

 life upon this planet can not be amiss. 



Among Lepidoptera the Rhopalocera constitute the highest 

 division of the suborder. The arrangement of A. S. Packard, Jr., in 

 his " Synthetic Types of Insects," seems to countenance no other 

 idea. The Heterocera embrace all that were formerly known as 

 Crepuscular and Nocturnal Lepidoptera. These terms, with that 

 of Diurnal, which were once applied to the entire suborder, though 

 strictly unnatural, subserve a good purpose. 



This arrangement harmonizes in a measure with their natural 

 sequence in time. If the highest types of life are the modified de- 

 scendants of pre-existent forms, then, from an evolutionary point 

 of view, Butterflies, which are assumed to be pre-eminent among 

 Lepidoptera, have sprung from the Bombycidse. There has un- 

 doubtedly been a gradual succession from certain Nocturnals to 

 Diurnals. 



There seems to be a tendency now-a-days upon the part of 

 naturalists to refer the entire animal creation to a primordial 



