MIGRATION AND DISPERSAL OF INSECTS : DRAGONFLIES. 153 



half a dozen or more on the leading shoot and ends of branches, 

 looked as if decorated with Chinese lanterns. Some few trees were 

 completely stripped of leaves. I examined carefully one small tree in 

 this condition, and found that it was killed, not directly by the moth, 

 but by the pine bark beetle, H. pinip('nla,v;h\ch already had numerous 

 burrows in the bark, and some eggs laid. Perhaps it is incorrect to 

 say it was already killed, but the beetles would soon dispose of any 

 remaining vitality, although their attack would have been impossible 

 but for the destruction of sap material by the caterpillars eating all 

 the leaves. The two insects together, therefore, destroy the tree, 

 though neither could do so by itself. 



Migration and Dispersal of Insects: Dragonflies. 



By J. W. TUTT, F.E.S. 

 Sharp dismisses (//;. sects, p. 425) the migration of the (hlonata in a 

 single short paragraph. He notes that " they are among the few 

 insects that are known to form swarms and migrate," and that 

 " swarms, usually consisting of species of the genus Lihcllula have 

 been frequently observed in Europe and America. Species of various 

 other genera also swarm, and a swarm may consist of more than one 

 species." 



Libiilula quadrimacHlata is probably the species most frequently 

 observed on its migration journeys in Europe. The estimated num- 

 bers comprising some of the swarms that have been reported by trust- 

 worthy observers frequently seem almost incredible. It is reported 

 that a large migration of L. qiiadrimaculata takes place almost every 

 year in the Charente-Inferieure from north to south. Wallace notices 

 that dragonflies came on board the "Adventure " frigate when fifty miles 

 off the coast of South America. Other observers have recorded the 

 capture of specimens of various species at sea many miles from the 

 nearest land. 



One of the earliest records of a large flight of dragonflies is that 

 made by the Abbe Chappe, Avho, in 1761, went to Siberia to observe 

 the transit of Venus. Whilst at Tobolsk, he states that a swarm of 

 some species of dragonfly passed the place, and he estimated its breadth 

 at five hundred ells and its length at five leagues. 



Meinecken reports that he once saw, in a village in Anhalt, on a 

 clear day, about four in the afternoon, such a cloud of dragonflies 

 {Libclli(li)ia) as almost concealed the sun, and not a little alarmed the 

 villagers, under the idea that they were locusts {Xatiirf<>rscltcr,\\., 110); 

 several instances are given by Rosel (vol. ii., p. 185) of similar 

 clouds of these insects having been seen in Silesia and other districts, 

 and Mr. Woolnough, of Hollesley, in Suffolk, a most attentive observer 

 of nature, once witnessed such an army of the smaller dragonflies 

 {Aijri(in) flying inland from the sea, as to cast a slight shadow over a 

 field of four acres as they passed. A migration of dragonflies was 

 witnessed at Weimar, in Germany, in 1816, and one, far more con- 

 siderable, and perhaps the greatest on record, occurred on May 80th- 

 31st, 1889, when cloud-like swarms of these insects (chiefly Lilullida 

 dcjircssa) were seen at Weimar, Eisenach, Leipzig, Halle, and Gottingen, 

 and the intervening country, extending over a large district {Ma'j. 

 Nat. Hist., n.s., iii., 516). 



