18 THE ENTOMOLOGIST. 



strong east wind blowing or a stiff south-wester, nor as a rule 

 before 10 a.m., nor after 4 p.m., except to sun themselves? I 

 should also like to know whether they consider that P. atalanta 

 immigrates in swarms or singly, whether they are supposed to 

 come from the east from Germany, Holland, and Belgium, or 

 from the south from France ? If they come from the east, they 

 can only come on an east wind, which they hate, and the 

 distance across the North Sea is too far for them to travel in a 

 day — and by night they do not fly. If they are supposed to 

 come from France in the spring, then any reference to meteoro- 

 logical records will show that in late spring or early summer 

 there are a very great number of days when a strong cold east 

 wind blows ; in fact, I have recollections of east winds prevailing 

 all through May. If the butterflies immigrate in swarms, then 

 surely some entomologist in North France must have noted the 

 gatherings preparatory to migration, in the same way that 

 swallows gather preparatory to their autumn flight abroad. If 

 it is contended that P. atalanta comes over by single individuals 

 in the spring, then what theory is advanced that it should only 

 enter the head of certain individual butterflies to migrate, and 

 must not the number of individuals be very great to admit of 

 their spreading over England ? 



I have previously stated that Dover, Malta, and the Channel 

 Islands are places on a regular line of migration for birds. Any 

 day during spring or autumn, about the time that certain birds 

 migrate, you will find those birds at Dover, Malta, and the 

 Channel Islands in places where you do not see them at any 

 other times. For instance, standing on the shore at Dover, one 

 can observe the swallows coming to land, and in my garden on 

 the outskirts of the town during the migrating season I have 

 seen numbers of warblers and small birds that live outside 

 towns. Now apply the preceding remarks to the migration of 

 P. atalanta. It can only arrive by day, during a limited number 

 of hours, from France, on a south-east to south-west breeze, not 

 too strong, at certain times of the year, and the sun must be 

 shining, and there must not be any abnormally large gathering 

 of the butterflies reported on the north coast of France. Given 

 the above conditions, has anybody noticed P. atalanta arriving 

 over the sea in sufficient quantities to spread all over England 

 and be the parents of the autumn specimens ? Personally I 

 have never noticed them, and for the five summers that I lived 

 at Dover I suppose I was on the cliffs or in a boat pretty well 

 every fine day that was possible, and I take it that Dover is the 

 most advantageous place possible in which to note the arrival of 

 " red admirals." I have noticed every year in my garden in 

 spring abnormal numbers of small birds immigrating and going 

 inland, but never abnormal numbers of P. atalanta, and yet the 

 autumn brood appears regularly. I always *' sugar " for P. ata- 



