BUTTERFLIES OF THE DISTRICT OF COLUMBIA 237 



Colias philodice. — The males have a rather strong odor, which is 

 constant and very uniform, resembling that of dried " sweet grass," 

 or of sweet hay. 



Phoebis eubule. — The odor of the males, which is very pronounced, 

 has been compared to that of violets, musk, Stephanotis, and Freesia. 



Pieris rapae. — The odor of the males is faint and difficult to detect. 

 It has been compared to that of mignonette and of SAveetbrier. 



Subfamily PAPILIONINAE 



PajrUio pMlenor. — The males have a sweet flowery odor somewhat 

 similar to that of the males of the parsnip swallowtail {PapiUo 

 polyxenes), but not so strong. The females have a strong and 

 disagreeable scent, pungent and penetrating, with a suggestion of 

 acetic acid. 



PapiUo glaucits. — ^The males have a sweet flowery odor, varying 

 from faint to fairly strong, which resembles that of the males of 

 the spicebush swallowtail {PapiUo froilus), though it is never so 

 pronounced. The females have a strong and disagreeable odor, 

 pungent or acid in character, which in some is very strong. 



PapiUo troilus. — The males of this species have the strongest odor 

 of all the local swallowtails. It exactly resembles that of certain 

 brands of honey biscuits. 



PapiUo polyxenes. — The males have a rather strong sweet odor 

 like that of carrot flowers, quite the same, apparentl}^, as that of the 

 very closely related European swallowtail {PapiUo viachaon). 



PapiUo marcellus. — The males have a spicy odor, intermediate 

 between that of the males of the other swallowtails and of the fritil- 

 laries {Argynnis cyhele and A. aphrodite). 



Family HESPERIIDAE 



No observations have been made on the odors of either sex of any 

 of the local skippers. 



EMANATIONS FROM BUTTERFLIES' WINGS 



Plates 59 to 64 



It has long been known that when placed in contact with a pho- 

 tographic plate in complete darkness the wings of butterflies affect 

 the plate in such a way that when the latter is developed a perfect 

 image of the wings is formed, the intensity of the image on the plate 

 being in general proportionate to the depth of the color on the wings. 

 In a print made from a negative prepared in this way the darker the 

 color on the butterfly the lighter will it appear in the print. 



