222 (October, 



ABSTRACT OF AN ARTICLE BY MONS. A. LANCASTER ON 

 MIGRATIONS OF LIBELLULA QUADEIMACULATA IN BELGIUM 



IN JUNE, 1900. 



WITH NOTES BY R. McLACHLAN, F.R.S., &c. 



[In June last Bel<i;ium was visited by extraordinary migratory 

 swarma of L. quadrimaculata. I had intimation of such having been 

 the case in a letter from my veteran friend Baron E. de Selys-Long- 

 champs, and his son, Baron Raphael de Selys-Longchamps, most 

 obligingly sent me his own copy of the Belgian Magazine, " Ciel et 

 Terre " for August 1st, which is mainly occupied by a carefully com- 

 piled paper (illustrated by a map) on the event by the editor, Mens. 

 A. Lancaster, Meteorological Director of the Belgian Observatory at 

 Uccle, and Member of the Belgian Academy. A translated abstract 

 of that paper cannot fail to prove interesting to English readers, and 

 the more so because M. Lancaster was enabled to obtain from his 

 observers information which it would have been difficult to collect 

 otherwise ; I would remark that the translation has been made freely, 

 and that portions have been omitted where they seemed of widely 

 general or locally special interest. — R. McLachlan]. 



" A phenomenon very rare in Belgium, and exceptional this time 

 by the extent of country embraced, and by intensity, was observed on 

 two occasions at the commencement of June last, the 5th and 10th. 

 It concerned the migration of compact swarms of the Dragon-fly 

 known as Lihellula quadrimaculata.^' 



"The migration of the 5th was noticed over a wide band occu- 

 pying all the central part of our territory, from the northern extremity 

 of the Province of Antwerp to a little over the French frontier in the 

 direction of Mens, limited in the west by Escaut, in the south-east by 

 the Province of Namur, to the east by the western part of the Pro- 

 vince of Liege, and to the north-east by Limbourg. The region in 

 which the insects were seen on June 5th extends from S.W. to N.E. 

 in a length of about 170 kilometres (106 miles), and from S.E. to 

 N.W. in a distance of 100 kilometres (62| miles)." 



" The migration of June 10th, partially continued on the 11th 

 and 12th, was entirely localized and confined to the coast. It was 

 not noticed inland. To the north it was noticed up to Holder, at the 

 northern extremity of Holland." 



" In both cases the migrations took place in the morning, and 

 each time in a direction op2)osed to that of the prevailing wind. This 

 seems of importance, because it has been already remarked with regard 



