1454 THE BUTTERFLIES OF NEW ENGLAND. 



but are otlicrwise of similar form, generally of some shade of green with 

 dusky clouds. 



"Dr. Curtis mentions the curious circumstance, that old specimens [of 

 this geiius] when alive have frequently lost one or both of their palpi, an 

 accident lie had only observed among the Pyralidae" (Westwood, Modern 

 class, ins., ii : 3(30). 



A fossil butterfly has been found in the miocene of Eott, Germany, 

 closely allied to this genus. 



EXCURSUS LVII.—NESTS AND OTHER STRUCTURES MADE 



BY CATERPILLARS. 



Uuweave the Caterpillar's gluey thread. 



Darwin.— TAe Botanic Garden. 



TiiEUE is considerable difterence among the caterpillars of butterflies as 

 to the amount of silk they spin. Some, and this is especially true of the 

 Lycaenidae, and next of the Pierinae, spin very little and have apparently 

 little use for it, being able to make their way about without weaving a 

 carpet whereon to cling, though they ordinarily do spin some. Others 

 seem unable to take a single step without laboriously spinning a thread 

 wherever they would go, fastening it upon this side and that, and without 

 it will venture nowhere. As a general rule nests of any sort are con- 

 structed only by the last named, i. e., by those most dependent upon a hold 

 on silken strands to make then- way. Yet there is one notable exception 

 in a Mexican Pierid which constructs a web nearly as close as parchment. 



Nests, which are almost solely for purposes of concealment, are very 

 generally made by those Ijutterflies whose caterpillars are gregarious, but 

 there is one kind made by New England social caterpillars which has no 

 such purpose and which is perhaps too simple to be properly called a nest. 

 Tliis is the web made, particularly in earlier life, by the caterpillars of 

 Euvanessa antiopa, which move about much from place to place, spinning 

 wherever they go, .so that at last the line of movement by successive 

 strands thrown across every angle a twig makes with the larger stem, forms 

 a sort of veil of silk over which they crawl with extreme rapidity, but with- 

 out which their movements are greatly retarded. 



Some caterpillars have a favorite place of repose to which they come 

 after every meal and which they carpet with silk for greater comfort. Of 

 such are some of the swallow-tails, and it would seem as if the nest they 

 construct were at first an accidental result of this habit, perfected by its 

 protective adaptation. These caterpillars rest upon the middle of the upper 

 surface of a leaf, upon the floor of which they have stretched a silken car- 

 pet from side lo side, each strand shorter than the last, so as to make the 



