48 PROCEEDINGS OF THE ACADEMY OF 



to it by necessity. As vegetable feeders they resemble caterpillars. 

 Suppose the stream in which some early caterpillars of caddice- 

 like habits and forms were residents, had become dried up, or 

 directed from its bed in such a manner as not to effect the removal 

 of the worms, and still leave the bed humid, there is no doubt that 

 those worms which possessed some advantage above their fellows, 

 better suited to the altered condition of affairs, would be preserved 

 and leave progeny. These would gradually, as time progressed, 

 become better adapted to their condition, giving rise to a higher 

 type of existence. A change in the specific gravity of their 

 environment would necessarily have the tendency, as an obviation 

 of the inconvenience thereby engendered, of producing changes 

 of habit on the assumption of pupation. This hypothetical case 

 would seemingly account for the habitudes of the Glaucopidians 

 and the Sphinges. 



Another explanation suggestive of the same idea presents'itself 

 for consideration. A scarcity of food might induce larva? well- 

 circumstanced in the " struggle for existence," to forsake their 

 habitual haunt, the watery element, for the land, as a preventive 

 to starvation. If slightly adapted to endure the change of habitat, 

 the effects of direct atmospheric influence associated with dietetic 

 causes, might so disturb their equipoise as to lead to a better ad- 

 justment of inner to outer actions, and thus be determinative of 

 the same results. 



While some of these larva?, in order to harmonize inner with 

 outer actions, or to restore as nearly as possible former modes of 

 living, on the attainment of pupa? may have passed into the 

 ground, others, doubtless, reached the same end by boring into 

 the stems of succulent plants, with or without a medulla, for cover 

 and protection, as well as for food ; some again, as if reluctant to 

 forsake their cases, the scenes of so many pleasures and adven- 

 tures in the past, carried their cases with them as many of our 

 Psychidae and Tineidse still do, until metamorphoses ensued ; 

 others again ceased gradually to encumber themselves therewith 

 during their larval existence, nature having provided them with 

 suitable protective appliances in the form of irritating hairs, 

 dangerous-looking, though perfectly harmless spines; offensive 

 fluids with equally offensive odors, and disgusting carneous quali- 

 ties ; to be only reassumed on the assumption of the chrysalis state, 



