238 



BULLETIN" 15 7, U. S. NATIONAL MUSEUM 



A series of experiments was undertaken with the object of adding 

 to our knowledge regarding this curious phenomenon. The follow- 

 ing 43 species were studied, all of which are native species except 

 for two swallowtails {Papilio parts and P. polycto?') from Siam and 

 a danaid {I tuna lainlrus) from Colombia : 



Neonympha eurytus (pi. 59, fig. 14). 



Basilarchia astyanax. 



Basilarchia archippus. 



Junonia lapinia (pi. 63, figs. 4, 5). 



Pyrcumeis virginiensis (pi. 62, figs. 



10, 11). 

 Pyrameis cardui (pi. 64, fig. 3). 

 Vanessa antiopa. 

 Polygonia interrogatlonis (pi. 59, figs. 



15, 16). 

 Phyciodes tharos (pi. 59, figs. 5, 6; pi. 



62, fig. 8). 

 Euphydryas phaeton (pi. 59, fig. 13). 

 Argynnis idalia (pi. 60, figs. 3, 4 ; pi. 



61, figs. 3, 4). 

 Argynnis cybele (pi. 60. figs. 1, 2; pi. 



61, figs. 1, 2; pi. 62, figs. 1, 2). 

 Danaus plcxippus (pi. 63, figs. 2, 3 ; pi. 



64, figs. 1, 2). 

 Ituna lamirus. 

 Chrysophanus phlaeas (pi. 59, figs. 17, 



18). 

 Everes oomyntas (pi. 62, fig. 9). 

 Lycaenopsis pseudargiolus. 

 Mitoura gryneus. 

 Eurema lisa. 



The preparation of these pictures is a very simple matter. The 

 wings, cut from the butterflies, are attached to pieces of paper, 

 black or white, with drops of shellac. A fresh box of plates is 

 opened in the dark room and the plates are removed. An old plate, 

 or a piece of glass of proper size, is placed in the bottom of the box 

 to form a firm and smooth backing for the paper with the wings, 

 which is laid upon it. Then a fresh plate is placed, emulsion side 

 down, upon the wings, another piece of paper with wings is placed 

 upon the upper (glass) surface of this plate, a second fresh plate 

 is placed, emulsion side down, upon these wings, and so on until all 

 the plates have been replaced in the box, which is then closed and 

 sealed and left in the dark room. 



The brightness of the image produced on the plate is proportion- 

 ate to (1) the length of exposure, (2) the degree of pressure against 

 the plate, and (3) inversely to the age of the specimen. 



Though very dark butterflies freshly caught will give fair results 

 after an exposure of from 24 to 30 hours on an ordinary plate — 



Colias eurytheme (pi. 59, figs. 11, 12). 

 Colias philodice (pi. 59, fig. 19). 

 Anthocharis genutia. 

 Pier is rapae (pi. 59, figs. 9, 10). 

 Papilio philenor (pi. 62, figs. 3, 5, 6; 



pi. 64, fig. 5). 

 Papilio polyxenes. 

 Papilio glaucus (pi. 63, fig. 1). 

 Papilio cresphontes. 

 Papilio troilus (pi. 62, fig. 4). 

 Papilio paris. 



Papilio polyctor (pi. 64, fig. 4). 

 Papilio marcellus (pi. 62, fig. 7). 

 Epargyreus tityrus. 

 Achalarus lyciades (pi. 59, figs. 7, 8). 

 Thanaos juvenalis. 

 Tlianaos martialis. 

 Thorybes daunus. 

 Thorybes pylades. 



Pyrgus tessellatus (pi. 63, figs. 6, 7). 

 Pontes vema. 



Erynnis leonardus (pi. 63, figs. 9-11). 

 Atrytone pontiac (pi. 59, figs. 3, 4). 

 Poanes massatsoit (pi. 59, figs. 1, 2), 

 Atalopcdes campestris (pi. 63, fig. 8). 



