NYMPITALIXAE: POLYfJOXTA COAnfA. 343 



skin upwards successively discoverini? the parts of the fully formed chrysalis, until at 

 last, and in scarcely more tiian one minute of time, tlie entire sl\in is gathered about 

 the anal feet. It noAV bends itself violently to disengage the end of the chi'ysalis' 

 which is long, pointed and hard, furnished with several little hooks, meanwhile retain- 

 ing its hold of the skin by the folds of its abdomen, until after a severe eftbrt, con- 

 vulsively reaching out and feeling in all directions for the object of its search, it 

 touches the button of silk and at once grasps it with its hooks and fixes them in it 

 securely. Then by a twisting iiiotion it manages to disengage the loose skin, which 

 falls to the ground, and the chrysalis rests. (Butt. N. Am., i.) 



Experiments made by Mr. Edwards in tlie application of cold to the 

 chrysalids of this species foiled from the death of the subjects. 



Parasites. I have never met with any hymenopterous parasites of the 

 caterpillar and find none on special record, but Mr. J. B. Smith says that 

 "not one in ten ever attains the butterfly state" on account of parasites, 

 and adds of his autumn collections that "the chrysalids I collected were 

 one and all infested." Mr. Ploward informs me the parasites were the 

 common Pteromalus vanessae (89:3). Glypta erratica Cress. (88:7) 

 has also been found parasitic on this butterfly by Dr. Kiley ; and I once 

 reared or had sent me a Tachinid fly and puparium raised from this S])e- 

 cies, but the fly has been lost. 



Desiderata. The accounts of the northern range of this butterfly are 

 so various, perhaps owing to its localization, that careful statements of its 

 comparative abundance are needed from all parts of Canada and the north 

 of New England, before its geographical distribution can be fully under- 

 stood. The cause of its localization also needs investigation and more 

 exact statistics are requisite in order to determine properl}" the history of 

 the insect, especially the duration of its several stages and the question of 

 its hibernation in the chrysalis state ; but of most interest of all would be 

 an enquiry into the precise relation of the two forms, dryas and harrisii, to 

 the two broods : a great many further statistics on this point, made in dif- 

 ferent places, are highly desirable. What dipterous parasite has it? 



LIST OF ILLUSTRATIONS.-POLYGONIA COMMA. 



Egg. . Imago. ^ 



PI. 64, tig. 18. Plain. P1.3, flg. 1. P. c. dryas male, both surfaces. 



19,20. Column of eggs. 3. P. c. harri.sii male, both surfaces. 



Catei-pillar. 4. P. c. dryas female, lower snr- 



Pl. 74, fig. 38. Side view, colored. face. 



78:36. Front view of head in final stage. '^- P- c. harrisii female, lower sur- 



81 : 9. Nest. face- 



86:67. Dermal appendage of bo<lv, stage i. 33:14. 31ale abdominal appendages. 



^,. „ „,. ' 38:10. Neuration. 



Chrysalis. „. ,« ^ , ,,,.,. 



r»i oo « o-» /-» .1- J, I 1* -J! .. 61:19. P. c. drvas. outline hmdwmg. 



PI. 83, fig. 27. Outlme of head from m front. „« x> ,' ... ,. ,. , . 



on nr, r^ ^,- j.- .1 . "0. P. c. uarrisu. outlmc hmd wmg. 



29, 30. Outlme ot mesothoracic 



tubercles. General. 



39, 46. Side view, colored. P'- ^*^' ^S- 2- Distribution in North America. 



47. Side view, outline. ^•'^- Glypta erratica, a parasite. 



48. Dorsal view outlijie. ^® • ^* Pteromalus vanessae, a parasite. 



