THE CANADIAN ENTOMOLOGIST. 157 



approach revealed the presence of vast numbers — I might safely say 

 millions — of these butterflies clustering everywhere. 1 counted a small 

 space, about the size of my two hands, on one of the trees, and there were 

 thirty-two butterflies suspended on it, and the whole group of trees was 

 hung in a similar manner. When disturbed, they flew up in immense 

 numbers, filling the air, and after floating about a short time, gradually 

 settled again. There appeared to be nothing on the trees to attract them, 

 yet when undisturbed they appeared at this time, to prefer resting in quiet, 

 as if enjoying the presence of congenial society. I regretted not having a 

 net with me, as I should like to have captured a number of them to see in 

 what proportion the sexes were represeted in the company. Their food 

 plants — the various species of Asclcpias — did not appear to be unusually 

 common in that section. I apprehended that many of the individuals 

 must have travelled some distance to be present at this gathering. The 

 fact that the larva of Archippus is but seldom affected with parasites may 

 partially account for their occasional abundance ; I only know of one 

 small ichneumon infesting them, and have seldom met with this. 



W. Saunders, London, (Jnt. 



Abundance oe I). Archippes in Massachesetts. — I wish to call 

 attention to the fact that Dana is archippus, Fab., is exceedingly common 

 all over New England this season. It is well known that many species of 

 our butterflies have a year of great abundance, and then are almost un- 

 known for quite a series of years. The cause of this is usually attributed 

 to a scarcity of insect enemies, and a favorable season for their food. 

 This abundance of a species is a sufficient reason for the multiplication of 

 parasitic enemies, which increase to the point of almost total extermina- 

 tion of the species attacked, as well as themselves. Two years ago, Cynthia 

 cardui was very abundant, and I obtained over one hundred larvae, not 

 one of which could I raise on account of a parasitic fly-larvae which were 

 so abundant as to lack food for their own maturity, practically extermin- 

 ating one another. Since then I have not seen a single cardui. Whether 

 the parasitic fly is common 1 am unable to say, I am confident that to 

 some extent the above is true of many species, btit D. archippus never has 

 to my knowledge any enemies, for this year I have raised abundance of 

 larvae and taken many chrysalids; but all were sound. Therefore we must 

 hunt for some other cause of their disappearance. Perhaps others more 

 interested in Lepidoptera than myself may have gathered facts which will 

 throw light upon this subject, and to draw out these experiences induces 



