THE PLAdJE OF CATERPILLARS.
[To THE EDITOR OF THE "SPECTATOR.") have had too little knowledge of the actual plague 'of caterpillars on the oak this year to venture on more than a conjecture of its cause, but though it seems probable that the mild and dry winter is insufficient to account for it, I incline to the opinion that weather, and not an unusual deficiency of in- sectivorous birds or other animal enemies, will be found to have been the chief cause of it, as I am convinced it is of most such outbursts. To account for these, you want some influence that is both very potent and very inconstant, and for this combination I know of none that is comparable with our weather; it is especially operative on the leaf-feeding insects in the winged stage, one which all have to get through, with generally a very short time in which to get through it. In the case of the carnivorous caterpillar of Cosmia trapezina, I have never found its numbers to vary greatly in different seasons. There is a graphic account of the way in which this caterpillar
runs down its prey, in Newman's "British Moths," p. 382.-1 am, Sir, 8ze.,
"It neither feigns death nor rolls in a ring when rudely dislodged by the beating-stick, but falls at full length into the umbrella, amid a shower of the other caterpillars, which the same stroke has also dislodged ; in this predicament it instantly catches sight of the first caterpillar that ventures to crawl, and starts in immediate pursuit, and an exciting race ensues, in which the Cosmia is not always the victor, the Cheimatobia [brumata, on which it principally feeds] sometimes escaping, through sheer superiority of speed ; the car- nivorous caterpillar, however, generally gains the day, and it is curious to observe that he does not seize the leaf-feeder by the binder part of the body, but never slackens his pace until his head is abreast of the other's neck, which he then seizes with savage eagerness, re- minding one strongly of a deerhound pulling down a stag, or at least of the representations of this cruel feat by the inimitable Landseer. When the first paralysing grip is given, it is all over with the leaf- feeder,—there is scarcely a struggle ; the Cheimatobia submits to its fate, and the Cosmia continues his repast until one wonders at his powers of consumption."—Newman's "British Moths," p. 382.
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