I4 6 STARLIGHT AND SUNSHINE. 



the family Lauracece, upon which it conceals itself in the neatly 

 folded leaf, as pictured. And yet I see that some collectors have 

 found it also on the prickly -ash, hop-tree (Ptelea\ and syringa. 

 Concerning the last mentioned, I can offer no explanation, but 

 the other two exceptions both in the Rue family have a some- 

 what interesting significance, taken in connection with the insect 

 next considered. The Ailantus silk -worm introduced into this 

 country from China about twenty years ago, and now very com- 

 mon in certain sections for years was not known to swerve in 

 its allegiance to its own companion, " tree of heaven." On the 

 basis of the facts already set forth, would any one doubt that if 

 its favorite food plant were suddenly exterminated there would be 

 a winged stampede, as it were, to the prickly- ash and hop-tree 

 (Ptelea}, the only two native allies to the Ailantus? But what 

 are the singular facts? The moth, I am told by careful observ- 

 ers, has quite recently proven fickle to its original diet, and yet 

 ignores the kindred plants. As a naturalized foreigner, under new 

 conditions, it has concluded to "do as the Romans do," and out 

 of compliment takes the lead of its closest insect ally, our Pro- 

 metkeus moth, whose favorite selections are the sassafras and its 

 relative the spice-wood, upon both of which the Ailantus is now 

 occasionally found. There certainly would seem to be some oc- 

 cult affinity between these two orders of plants, Lauracecs and 

 Rutacece, which the botanists have not discovered. 



The exceptions, however, only emphasize by contrast the infi- 

 nite number of almost infallible instances, enforcing the irresisti- 

 ble deduction of an original universal law of botanical distinction 

 among the insect tribes. These lapses, if not instances of mere 

 temporary aberration eventually to be discountenanced by the 

 "survival of the fittest," may perhaps be significantly associated 

 with these remarkable freaks of transition noted by collectors 

 those strange dissimilar double broods of the same insect in which 

 some scientists discover the pioneers of newly created species.* 



* In the " Semicolon," for instance, which I have shown to lapse occasionally 

 in its botany, and the Alope butterfly and many others, the two succeeding broods 



