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MIGRATION OF PIERIS BRASSIC^ OBSERVED 

 AT HARWICH. 



l!y F. KERRY. 



'T^HERE has been, this summer, an immense immigration of 

 "^ Fieris brassicce from tlie Continent to this portion of the 

 east coast. On Thursday, the iith of August, and for several 

 days after, large numbers of this butterfly were to be seen coming 

 over the sea, and many were drowned in the water. The lobster 

 catchers, who fish about five or six miles from the shore, told me you 

 could not look anywhere over the sea without seeing white butterflies 

 making for the shore, all coming from the S.E. and flying N.W. At 

 Harwich thousands of the Fieris could be observed in the gardens 

 busily depositing their eggs, with dire consequences to the vegetables. 

 The resulting larvce must have been present in millions. Nearly all the 

 broccoli, cabbage, savoys, and brussel sprouts were eaten up, nothing 

 remaining of the plants but the main ribs. 



No one in this neighbourhood remembers a similar visitation 

 before. Ichneumons (probably Apanteks glomcratiis, L.) have 

 destroyed the greater part of the larvce in some gardens. At the 

 " Phoenix Hotel," Dovercourt, quite four-fifths of the caterpillars 

 were so destroyed; while at the Trinity Houses, about two hundred 

 yards off, the piipcv are in considerable excess of the yellow patches 

 of Ichneumon cocoons; I took 250 pupa there in about ten 

 minutes, thus demonstrating the prodigious numbers of the insects. 



[We have pleasure in giving prominence to Mr. Kerry's note, 

 inasmuch as such observations have an important bearing upon all 

 theories of the distril)ution and erratic appearance of various species of 

 insects in Britain. There can be little doubt that many of our 

 insects, such as the Coiias, Parameus cardui, Flusia gamma, and others 

 which appear occasionally in great numbers, and may then disappear 

 or become very rare for years together, are migratory ; and that the 

 specimens which occasionally delight our eyes in numbers are 

 either immigrants or the immediate offspring of immigrants from the 

 Continent. More than twenty years ago the immense swarms of 

 '"Lady-bird" beetles {Cocinelia) which made their appearance on 

 parts of the English coast attracted much popular attention, and led 

 to alarming outbursts of " newspaper science." Several direct 

 observations of immigration of insects into England are on record. 

 A very remarkable instance was given in The Essex Naturalist for 

 1888 (vol. ii., p. 158), the insect being a Dragon-fly {Libellula 

 guadrimaculaia) observed off the Essex coast near Shoebury- 

 ness. — Ed.] 



