IMPEKFECT SOCIETIES OF INSECTS. 



7 



Westw., a native of Van Diemen's Land, exhibited a sin- 

 gular migrating propensity as described by Thomas I. Ewing, 

 Esq., who has given them the name of the "migrating 

 caterpillars." Passing, about December 20th, from a barley 

 field which had been ploughed up, and which seemed lite- 

 rally in motion with them, they proceeded up the road, 

 entered at the gateway into the lawn, then crossed the ve- 

 randah in front of the house, and through two gardens until 

 they reached a field laid down with English grasses, on which 

 they committed sad havoc. Many of them did not stop there, 

 as the whole road from the field to the town was black with 

 them. They did not cease migrating for a fortnight, pro- 

 ceeding with a quick and almost running motion over every 

 obstacle, whether walls or shrubs, &c, and making a sudden 

 halt at noon Avherever they chanced to be, and reposing in 

 that spot till four the next morning, when they were again 

 in motion. 1 It is probable that these caterpillars were in 

 search of fresh pasture like others feeding on trees, of which 

 instances are on record of a whole army having at once 

 quitted a forest of which they had entirely consumed the 

 leaves in quest of another. One of these hosts (as we may 

 conclude) is stated by an American newspaper, the Charleston 

 Courier, to have availed themselves in May, 1842, in passing 

 from Richland to the St. Mathew's shore, of a new railway 

 there running over the Cangaree Swamp, as a convenient 

 bridge, in such countless swarms that a solid column of them 

 filled the railway for upwards of a mile, and actually arrested 

 the course of a locomotive drawing a full train of waggons 

 laden with iron, though moving with a speed of ten to 

 twelve miles an hour, and which was only able to proceed by 

 throwing sand on the fore wheels. 



But of insect emigrants none are more celebrated than the 

 locusts, which, when arrived at their perfect state, assemble, 

 as before related, in such numbers, as in their flight to in- 

 tercept the sunbeams, and to darken whole countries, passing 

 from one region to another, and laying waste kingdom after 

 kingdom; but upon these I have already said much, and 



Trans. Ent. Sac. Lond. ii. proc. lvi. 

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