1352 THE BUTTERFLIES OF NEW EN(iLAND. 



and relatively less both in the Lycaenidae and Papilionidae, there being 

 four in the former, or, approximately in one out of every five species, and 

 three in tlie latter, or one in every five ; while in the Hesperidae there are 

 but two instances brought to light, or only one for every twenty-three 

 species. If we analyze the Nyniphalidae more closely, we find the cases, 

 with one exception, confined to the Nymphalinae and distributed as follows, 

 mentioned in the order of their relative importance : Argynnidi, five out 

 of eight species ; Melitaeidi, three out of five species ; and Vanessidi, 

 four out of thirteen species. 



Here it may be observed that the Argynnidi and Melitaeidi, in which 

 the relative numl>er far exceeds the others, are more than almost any other 

 tribes of butterflies, characteristic of the temperate i-egions of the earth ; 

 and in entire keeping with this fact is another, that examples of suffusion 

 are almost exclusively confined to the temperate zone ; that this is not due 

 to a more thorough search of temperate regions is clear, because from no 

 quarter of the globe are butterflies more eagerly sought than from the 

 tropics, and the sutfusiou of butterflies in temperate regions is sufticiently 

 common to be now known in nearly one-fifth of our species ; I have 

 myself seen nearly fifty suffused examples of our common Heodes hypo- 

 phlaeas. 



These facts point to cool temperature as a cause for such phenomena, 

 and this presumption is strengthened by the relatively frequent occurrence 

 of suffused specimens in the Alps of Switzerland and in spring broods of 

 butterflies. It would be well to note the day of capture and elevation of 

 the locality in every known case of suffusion to see how fairly this conclu- 

 sion may be held ; and to learn at what period in the life of the insect the 

 cold must be present to effect this result. In experiments of the applica- 

 tion of cold to chrysalids, such suffusions have been artificially produced, 

 and this would seem to point to this as the direct cause ; but it may be 

 that cold in the larval period, inducing lethargy and so insufficient nour- 

 ishment, may be equally effective, for the late Mr. Elliot states (Science, 

 ii:353) that insufficient food given to caterpillars of Euvanessa antiopa 

 resulted in sports which varied decidedly in the direction of the completely 

 suffused type E. a. hygaeia. 



It may be convenient here to tabulate the species of our own fauna in 

 which suffused varieties have been found : — 



JSfymphalidae : Polygonia satyrus, Euvanessa antiopa, Aglais milberti, 

 Vanessa cardui ; Speyeria idalia, Argynnis cybele, A. atlantis, Brenthis 

 myrina, B. bellona ; Phyciodes tharos, Cinclidia harrisii, Euphydryas 

 phaeton; Anosia plexippus. Lycaenidae : Incisalia irus, Thecla lipa- 

 rops ; Cyaniris pseudargiolus ; Heodes hypophlaeas. Papilionidae: 

 Eurymus philodice ; Euphoeades troilus, Papilio polyxenes. Hesperidae: 

 Epargyreus tityrus ; Thymelicus mystic. 



