M. Hubert on an Emigration of Butterflies. 34T 



ed with astonishment the inconceivable numbers of these in- 

 sects in the districts of Grandson and Yverdun, and what 

 made it more singular, it was not the time when they used 

 generally to appear, which was at the end of summer and au- 

 tumn ; they were also larger and more beautiful than they 

 commonly are, from the brilliancy and fine preservation of 

 their colours. I found a great number at the foot of the 

 mountains, and upon the Jura, where their brilliant appear- 

 ance contributed not a little to the embellishment of nature. 



These butterflies dispersed among the flowers did not ap- 

 pear to have amongst them any other connection but the 

 sexual one. 



These caterpillars were from that time well known. They 

 not only found their food upon the thistles and artichokes, 

 but the viperine and the leaves of the passeroses were attack- 

 ed. 



Here then is a new fact simply stated. One of the most 

 beautiful species of our butterflies comes to us from the south ; 

 it flies in a close column, expands through our country, and 

 spreads probably as far as Germany ; but are these emigra- 

 tions frequent, are they annual ? The letter of the learned 

 Italian naturalist says, that they had already seen this pheno- 

 menou a few years before in Piedmont. 



We ought not to infer, from their, irruption towards the 

 north, that they emigrate again to our climate in autumn, or 

 that their natural multiplication is not great enough to give an 

 equal increase. These migrations, then, do not resemble 

 those of birds of passage ; nevertheless, in our complete igno- 

 ranee of all the causes and motives which determine them, 

 it is proper to gather the facts which relate to them, and 

 carefully to study all the circumstances. The naturalists of 

 the countries who read our memoirs are invited to commu- 

 nicate their analogous observations. It will be very inte- 

 resting to know how far the multiplication and existence of 

 this species extended into the south, to know exactly where 

 they came from, in the first place, in what place they are 

 most common, why they quitted it, &c. &c. 



The answer to these questions will form one of the most 

 curious chapters in the history of insects. 



