1900] 223 



to a migration observed uear Ghent about June 21st, 1860, when the 

 insects flew from S.W. to N.E., the weathercock indicating N.E." 



" During the migration of June 5th last the direction of the wind 

 in the western part of the kingdom was N.W. to N.N.W. ; but ac- 

 cording to the great majority of the accounts collected the Dratjon-flies 

 flew in an average direction of S.E. to N.W., thus contrary to the 

 wind, which blew at the force of about 4 to 5 metres per second." 



" On June 10th the creatures came from the sea, and, as on the 

 5th, went against the wind, which was S.S.E. to S.E., with a force of 

 4 metres." 



"All the observers agree in stating that the insects flew rather 

 low, with astonishing regularity, and without resting ; that they kept 

 close to the earth where there were no obstacles, but that they mounted 

 to a height of 10 to 12 metres when houses and trees were in their 

 way ; they did not go round obstacles in their line of route, but sur- 

 mounted them and descended on the other side." 



" According to some observers their flight was rather slow ; others 

 again asserting that it was very swift. At Uccle and Wetteren, lo- 

 calities placed on a line from S.E. to N.W., one could estimate the 

 velocity of flight at 5 metres per second, or 18 kilometres (Hi 

 miles) per hour." 



" In general they went in groups more or less isolated and more 

 or less dense. At Uccle, according to Messrs. Vincent and Vander 

 Linden, of the Observatory, some were constantly in sight, and some- 

 times 10 together ; but in other localities, such as Antwerp or in the 

 Borinage, the groups were extremely compact at certain moments." 



" On June 5th the first individuals appear to have been seen at 

 7 a.m. The time of maximum frequency was from 10 a.m. to noon 

 according to locality, and the latest hour was in general 2 to 2^ p.m. 

 On the Escaut, however, according to an observation of M. Van 

 Heurck, Director of the Botanical Gardens at Antwerp, belated in- 

 dividuals were seen up to 4 and 5 p.m. He says that the captain of 

 his yacht, moored midway between Antwerp and Burght, reported 

 that between 2 and 3 p.m. the insects were in such numbers that the 

 air appeared black ; towards 4 to 5 p.m. there were still isolated 

 individuals. More than that, M. F. Jacobs, President of the Belgian 

 Astronomical Society, at his chateau to the north of Termonde, wit- 

 nessed the migration as late as 7 p.m. He says he is certain that at 

 that hour the flight was less regular, the insects flew in masses slighty 

 separated, frequently touching the hay, and appearing as if they wished 

 to stop for the night. But they did not fix themselves definitely, and 



