IMPERFECT SOCIETIES OF INSECTS. 329 



at noon wherever they chanced to be, and reposing in that spot till four 

 the next morning, when they were again in motion.^ 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 loco- 

 motive 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 fliglit to intercept 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 

 shall have occasion again to enlarge. The same tendency to shift their 

 quarters has been observed in our little indigenous devourers, the Aphides. 

 Mr. White tells us, that about three o'clock in the afternoon of the 1st of 

 August, 1785, the people of the village of Selborne were surprised by a 

 shower of Aphides or smother flies, which fell in those parts. Those that 

 walked in the street at that juncture found themselves covered with these 

 insects, which settled also upon the hedges and in the gardens, blackening 

 all the vegetables where they alighted. His annuals were discolored by 

 them, and the stalks of a bed of onions quite coated over for six days 

 after. These armies, he observes, were then, no doubt, in a state of 

 emigration, and shifting their quarters, and might have come from the 

 great hop plantations of Kent or Sussex, the wind being all that day in 

 the east. They were observed at the same time in great clouds about 

 Farnham, and all along the vale from Farnham to Alion.- A similar 

 emigration of these flies I once witnessed, to my great annoyance, when 

 traveling later in the year, in the Isle of Ely The air was so full of 

 them, that they were incessantly flying into my eyes, nostrils, &.c., and 

 my clothes were covered by them. And in 1814, in the autumn, the 

 Aphides were so abundant for a few days in the vicinity of Ipswich, as 

 to be noticed with surprise by the most incurious observers ; as they were 

 September 26th and 27th, 1836, at Hull, where, as the local newspapers 

 stated, such swarms filled the air that it was impossible to walk with com- 

 fort from their entering the eyes and mouth at every step ; and on the 

 same days they were equally numerous at York and Derby. 



As the locust-eating thrush (Turdus Gryllivorus) accompanies the 

 locusts, so the lady-birds (Coccinella) seem to pursue the Aphides ; for I 

 know no other reason to assign for the vast number that are sometimes, 

 especially in the autumn, to be met with on the sea-coast, or the banks 

 of large rivers. Many years ago, those of the Humber were so thickly 

 strewed with the common lady-bird (C. septempunctata) , that it was diffi- 



» Trans. Ent. Soc. Land. ii. proc. Ivi. * Nat. Hist. ii. 101, 



28* 



