A great discussion has arisen as to the reason of
the plague of caterpillars which appear to be destroying our British oaks. Some say that it is the deficiency of the insect-eating birds which causes the plague, while others maintain that it is the sickliness of the trees which renders them liable' to this plague, and that that sickliness was caused in 1881 by the severity of the two previous winters, but in 1882 by the fierce gale of April 29th, which certainly seared the horse-chestnuts and hawthorn trees on the side on which it struck them almost as if it had been rather flame than wind. We doubt both explanations. It is certainly trite that, on the whole, the little birds have been unusually numerous this spring, instead of unusually deficient,—for which, no doubt, we have to thank Mr. Dillwyn's Wild Birds' Act; so that it is hardly possible to account for the increase of the cater- pillars by the decrease of their hereditary foes. And again, it is not at all easy to suppose that a wind which did not seriously injure either the beech, the elm, or the lime, should have taken such effect on the oaks as to have more than compensated for the mild winter. Perhaps some "protective" variation has taken place in this destructive oak-leaf caterpillar which makes it unpalatable to the insect-eating birds, but this guess is so disagreeable and ominous, that we earnestly hope that it may be false. It is a plain duty to let all the young rooks and bull- finches of this generation grow to maturity, and see what they may be able to effect in the way of making war on the oak caterpillars.
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