DO BUTTERFLIES MIGRATE? 



FIVE HUNDRED MONAKCII lUTTEHFLIES IN A NEW AllSKUM GKOUP THAT 

 ILLrSTHATES THE SOCIAL INSTINCT OF THE SPECIES 



Bi/ Frank K. Lufz 



THE animal migration of birds is a fact of everyday knowledge. 

 Similar migrations of other animals svich as certain fish are also 

 fairly well-known, Init very few cases of definite migrations of 

 insects have come to the attention of entomologists even. One of the most 

 striking of these cases occurs in this part of the world every year and the 

 preparatory swarming is illustrated in a gronj) just installed in the hall of 

 insect biology. 



The larvte of the monarch butterfly (Auosia jjli-.rippus) feed during the 

 summer on ^•aI•ious species of milkweed, protected from insect-eating birds 

 by their "warning colors" which are thought to advertise the fact that they 

 are ill-tasting, acrid creatures. The adults emerge in the fall in great num- 

 l)ers from beautiful green chrysalids decorated with black and gold, and 

 these butterflies also are gaudy in coloring and are inedible. 



Now, the mourning cloak (Kiirdui.s.sa aiifiojHi) and certain other butter- 

 flies do pass the winter with us as adults so that there would seem to be no 

 reason in external conditions why the monarchs could not. In the early 

 autumn however they begin to flutter southward and in this movement 

 many hundreds or e\-en thousands of indi\i(luals fly together, often remain- 

 ing in one locality for several days. Curiously enough, certain definite 

 resting places, or gathering ])laces, seem to be used year after year. Such 

 an one is near Clinton, Connecticut, where the sj)ecimens for a Mu.seum 

 group were obtained in the fall of H)!!. The swarming l)utterflies are so 

 numerous and clustered so thickly that the leaves are obscured and the 

 brownish undersides of the wings of tin- resting buttcrflii-s give to the trees 

 a truly autinnnal appearance. 



Then comes the continuance of the southward flight. In places the 

 air is brown with fluttering l)Utterfiies. As they reach the more southern 

 states they doubtless spread out ovcm- the coimtry again, but we are indeed 

 ignorant as to how far th()S(> individuals which were born in New England 

 for instance, really go, how they spend the winter, or from whence the 

 monarchs of the next New England spring come. No one has put on record 

 a return flocking from the South, so that if there be a migration northward 

 it would seem to be only by stragglers. Furthermore the specimens found 



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