The remarkable part of the business is that the greenhouse caterpillars do not venture out of their nests either. And yet for them there are no boughs dangerously shaken, no cold piercing beyond endurance, for it is not freezing under the glass. What keeps them in can be only the passage of that wave of depression. On the 15th the storm ceases; and the barometer remains between 29.6 and 30 in. for the rest of the month and a good part of February. During this long period there are magnificent sorties every evening, especially in the greenhouse. On the 23rd and 24th of February, suddenly the Processionaries stop at home again, for no apparent reason. Of the six nests under cover, only two have a few rare caterpillars out on the pine-branches, while previously, in the case of all six, I used every night to see the leaves bending under the weight of an innumerable multitude. Warned by this forecast, I enter in my notes: “Some deep depression is about to reach us.” And I have guessed right. Two days later, sure enough, the meteorological record of the Temps gives me the following information: a minimum of 29.2 in., coming from the Bay of Biscay on the 22nd, reaches Algeria on the 23rd and spreads over the Provence coast on the 24th. There is a heavy snowfall at Marseilles on the 25th. “The ships,” I read in my paper, “present a curious spectacle, with their yards and rigging white. That is how the people of Marseilles, little used to such sights, picture Spitzbergen and the North Pole.” Here certainly is the gale which my caterpillars foresaw when they refused to go out last night and the night before; here is the centre of disturbance which revealed itself at Sérignan by a violent and icy north wind on the 25th and the following days. Again I perceive that the greenhouse caterpillars are alarmed only at the approach of the wave of atmospheric disturbance. Once the first uneasiness caused by the depression had abated, they came out again, on the 25th and the following days, in the midst of the gale, as though nothing extraordinary were happening. From the sum of my observations it appears that the Pine Processionary is eminently sensitive to atmospheric vicissitudes, an excellent quality, having regard to his way of life in the sharp winter nights. He foresees the storm which would imperil his excursions.