172 PREVENTING THE ATTACK OF INSECTS, MILDEW, Ac. 
mence spinning webs; they cannot then eat the epidermis of the leaves, 
and they require some protection from the cold and rain, which their 
tender frames are not yet fitted to endure ; to effect which they mine 
into the leaves, eating the parenchyma only, and leaving the cuticle 
untouched. Having acquired sufficient strength to hear the changes 
of weather, and eat every part of the leaves, they make their way out ; 
and the anxious gardener, who has hitherto only observed the brown¬ 
ness of the leaves caused by the mining, but which is attributed to the 
blasting effects of an easterly wind, is astounded to see myriads of 
caterpillars swarming on the trees, disleafing every branch as they 
proceed. The fact of their mining sufficiently explains the reason of their 
sudden appearance; it shows how, in one day, not a single caterpillar 
may be visible on the trees, and the next they may be swarming with 
larvae of so large a size as to rebut the idea of their having been recently 
hatched. Besides, their latter habit of feeding on the leaves exter¬ 
nally is so little like their former one of feeding on them internally, 
that any one who has not satisfied himself by examination that both 
habits are proper to the same caterpillars would scarcely suppose this 
to be the case. While the caterpillars are within the leaves they are 
of a yellowish colour, though they become darker at each change of 
skin. It is in this state that Mr. Lewis advises their destruction by 
gathering and burning every leaf which shows their internal depreda¬ 
tions. Their nests are so difficult to discover, that searching for them 
seems out of the question; and if a wash strong enough to dissolve 
their glutinous covering were applied, it would probably at the same 
time injure the tree. Having eaten their fill, they prepare for the 
pupa state, by spinning strong cocoons of a long oval shape. In a 
short time they come forth in their perfect winged form, and may be 
seen on mornings and evenings flying in great numbers round the 
devoted trees which are in the following year to be the scene of similar 
ravages, unless circumstances for which we cannot account should pre¬ 
vent their multiplication.” 
This same little moth is also partial to the foliage of the hawthorn; 
whole hedges may be often seen stripped of leaves, and covered by the 
webs of the caterpillars. The same or other sorts of larva) mine the 
leaves of the lilac, cow-parsnep, and several other plants. 
I have thought well to transcribe the principal part of Mr. Lewis’s 
paper, not only because it is a very satisfactory account of the Ypono- 
menta padella, but because it conveys an excellent idea of the breeding 
and various transformations of moths in general; I would further 
observe, that his mode of destruction, though effectual as far as it goes, 
strikes me as impracticable. To gather every infected leaf would be a 
