LIBELLULID^ — DRAGON- FLIES. 139 



their first stages in, water, Wasser-jungfern — Virgins of the 

 Water. Another German name for them is Florfliegen — 

 Gauze-flies, in allasion to their net-like wings. Oar boys 

 also call them Snake-feeders and Snake-doctors, in the be- 

 lief that they wait upon snakes in the capacity of feeders 

 and doctors; and so firm are they in this belief, that fre- 

 quently I have been laughed at for asserting the contrary 

 to them. The belief probably arose from the manner in 

 which the Dragon-fly sometimes falls a prey to the snakes. 

 Hovering over ponds, they are fond of alighting on little 

 sticks and twigs just out of the water, and mistaking the 

 heads of snakes, which probably swam there for the purpose, 

 for such twigs, they are instantly caught by the snakes. 



On the 30th and 31st of May, 1839, immense cloud-like 

 swarms of Dragon-flies passed in rapid succession over the 

 German town of Weimar and its neighborhood. They were 

 the Libellula depressa, a species which, in general, is rather 

 scarce in that part of Germany. The general direction of 

 this migration was from south by west to north by east. 

 The insects were in a vigorous state, and some of the flocks 

 flew as high as 150 feet above the level of the River Ilm. 



At Gottingen on June the 1st, at Eisenach on May the 30th 

 and 31st of the same year, swarms of the same species were 

 seen flying from east to west; and at Calais, June 14th, 

 similar clouds, though of a different species, were noticed 

 on their way toward the Netherlands. At Halle, also, on 

 May 30th, a short time before a thunder-storm, swarms of 

 the Dragon-fly, L. quadrimaculata, were seen by Dr. Buhle, 

 flying very rapidly from south to north. The L. quadri- 

 maculata is not generally found in the neighborhood of 

 Halle. 



This wonderful migration, for it is a phenomenon of rare 

 occurrence, extended from the 51st to the 52d degree of 

 latitude, and was observed within 27° 40' and 30° east of 

 Ferro. But the instance of Calais renders it probable that 

 it extended over a great part of Europe. 



Another migration of Dragon-flies was observed at 

 Weimar on the 28th of June, 1816. The insects, in this 

 instance, belonged also to the L. depressa. They were 

 taken then, as were they also in 1839, for locusts by the 

 common people, and looked upon as the harbingers of fam- 

 ine and war. 



In these migrations they followed the direction of the 



