130 



it must be remembered that the species are all Arctogaeal. While 

 ,both genera are Bombyciform iSToctuidae, it seems natural that they 

 should favor high latitudes, and H. scripta may be spreading south- 

 wards on this continent. We have it from Virginia, but I have 

 already remarked that the lepidopterous fauna of the Southern 

 States is not divisible from the Middle States, until, perhaps, we 

 come to the Floridian peninsula and Southern Texas. Hence I 

 would attach little value to descriptions of species princiiially based 

 on Southern localities, e. g., Grapta Cramer i, Scudder. I have the 

 Floridian Harveya auripennis, also from Kentucky; this seems to 

 me a Southern form spreading northwards, since the group to which 

 it belongs is more extensively developed as we progress towards the 

 equator. 



Acronycta lepusciiliua, Gucnee. 



Habitat, California (Mr. Hy. Edwards, No. 72). 



Two specimens are before me which are better marked beneath 

 than usual, but which belong evidently to this species. This must 

 not be confounded with A. lupini, Behr. A study of this genus 

 shows that the specific names retained under it represent very une- 

 qual values. Thus, Acronycta occidentalis, Grote, designates a form 

 which differs exceedingly slightly in the imago state from another, 

 Acronycta psi, while the two species differ very strongly as larvae 

 or in the young stage. Again, Acronycta lobeliae, Gucnee, repre- 

 sents a form that, comparatively speaking, cannot be mistaken in 

 any stage, as far as known. Yet where Ave find a difference we are 

 obliged to signalize it, the rather if we are amenable to the eviden- 

 ces offered by the theory of evolution of species through constantly 

 acting natural laws. AYhere, as in Acronycta, there is a prevailing 

 general uniformity in the appearance of the images of a single 

 group of species, and generally broad distinctions between the lar- 

 val forms, it is a not unreasonable conclusion that these larval 

 differences are gradually evolved by the workings of a natural pro- 

 tective law which intensifies their characters in the direction in 

 which they are serviceable to the continuance of the animal. 



Understanding metamoi-phosis in insects as correlated with devel- 

 opment, and as a growth -period characterizing a more sudden 



