174 



INDIRECT INJURIES CAUSED BY INSECTS. 



they swarm ; on the wing they darkened the air, and pro- 

 duced a sound like that of distant drums. ^¥hen they were 

 feeding, the noise of their jaws might be mistaken for the 

 sawing of timber. Travellers and people abroad were very 

 much annoyed by their continual flying in their faces ; and in 

 a short time the leaves of all the trees for some miles round 

 were so totally consumed by them, that at midsummer the 

 country wore the aspect of the depth of winter.^ 



But the criminals to whom it is principally owing that our 

 groves are sometimes stripped of the green robe of summer 

 are the various tribes of Lepidoptera, especially the night- 

 fliers or moths, myriads of whose caterpillars, in certain 

 seasons, despoil whole districts of their beauty, and our walks 

 of all their pleasure. Some of these, like the cockchafers, 

 or the caterpillars of Clisiocampa neustria, Porthesia cliry- 

 sorrhcea, &c. before mentioned, as attacking most fruit-trees, 

 are also general feeders on forest trees, though some of the 

 species usually prefer particular kinds when accessible. Thus 

 in 1731 the oaks of France were terribly devastated by the 

 larva of Hypogymna dispar^ ; as are often those of Germany 

 by that of Cnetliocampa processionea ; and those of England 

 by the leaf-rolling caterpillar of the pretty little green moth 



1 Philos. Trans, xix. 741. 



2 Reaum. i. 387. These larvas were so extremely numerous in 1826 on the 

 lines of the Alle Verte at Brussels, that many of the trees of that noble avenue, 

 though of great age, were nearly deprived of their leaves, and afforded little 

 of the shade which the unusual heat of the summer so urgently required. The 

 moths which in autumn proceeded from them, when in motion towards night, 

 swarmed like bees, and subsequently on the trunk of every tree might be seen 

 scores of females depositing their down-covered patch of eggs. In the Park they 

 were also very abundant ; and it may be safely asserted that if one half of the 

 eggs deposited were to be hatched, in 1827 scarcely a leaf would remain in either 

 of these favourite places of public resort. Happily, however, this calamity was 

 prevented by natural means. Of the vast number of patches of eggs which I saw on 

 almost every tree in the park about the end of September, I could two months 

 afterwards, to my no small surprise, discover scarcely one, though the singularity 

 of the fact made me examine closely. For their disappearance I have no doubt 

 the inhabitants of Brussels are indebted to the tit-mouse (Parws), the tree-creeper 

 ( Certhia familiaris), and other small birds known to derive part of their food from 

 the eggs of insects, and which abound in the Park, where they may be often seen 

 running up and down the trunks of the trees, at once providing their own food 

 and rendering a service to man, which ail his powers would be inadequate com- 

 pletely to effect. 



Reaumur (ii. 106.) in certain seasons found these patches of eggs so numerous, 

 that in the Bois de Boulogne there was scarcely an oak, the under side of the 

 branches of which were not covered by them for an extent of seven or eight feet. 

 He informs us that the eggs are not hatched till the following spring. 



