The appearance of the campos changes very much according to the season.There is not that grand uniformity of aspect throughout the year which is observed in the virgin forest, and which makes a deeper impression on the naturalist the longer he remains in this country.The seasons in this part of the Amazons region are sharply contrasted, but the difference is not so great as in some tropical countries, where, during the dry monsoon, insects and reptiles go into a summer sleep, and the trees simultaneously shed their leaves.As the dry season advances (August, September), the grass on the campos withers, and the shrubby vegetation near the town becomes a mass of parched yellow stubble.The period, however, is not one of general torpidity or repose for animal or vegetable life.Birds certainly are not so numerous as in the wet season, but some kinds remain and lay their eggs at this time--for instance, the ground doves (Chamaepelia).The trees retain their verdure throughout, and many of them flower in the dry months.Lizards do not become torpid, and insects are seen both in the larva and the perfect states, showing that the aridity of the climate has not a general influence on the development of the species.Some kinds of butterflies, especially the little hairstreaks (Theclae), whose caterpillars feed on the trees, make their appearance only when the dry season is at its height.The land molluscs of the district are the only animals which aestivate; they are found in clusters, Bulimi and Helices, concealed in hollow trees, the mouths of their shells closed by a film of mucus.The fine weather breaks up often with great suddenness about the beginning of February.Violent squalls from the west or the opposite direction to the trade-wind then occur.They give very little warning, and the first generally catches the people unprepared.
They fall in the night, and blowing directly into the harbour, with the first gust sweep all vessels from their anchorage; in a few minutes a mass of canoes, large and small, including schooners of fifty tons burthen, are clashing together, pell-mell, on the beach.I have reason to remember these storms, for Iwas once caught in onemyself, while crossing the river in an undecked boat about a day's journey from Santarem.They are accompanied with terrific electric explosions, the sharp claps of thunder falling almost simultaneously with the blinding flashes of lightning.Torrents of rain follow the first outbreak; the wind then gradually abates, and the rain subsides into a steady drizzle, which continues often for the greater part of the succeeding day.
After a week or two of showery weather, the aspect of the country is completely changed.The parched ground in the neighbourhood of Santarem breaks out, so to speak, in a rash of greenery; the dusty, languishing trees gain, without having shed their old leaves, a new clothing of tender green foliage; a wonderful variety of quick-growing leguminous plants springs up; and leafy creepers overrun the ground, the bushes, and the trunks of trees.
One is reminded of the sudden advent of spring after a few warm showers in northern climates; I was the more struck by it as nothing similar is witnessed in the virgin forests amongst which I had passed the four years previous to my stay in this part.The grass on the campos is renewed, and many of the campo trees, especially the myrtles, which grow abundantly in one portion of the district, begin to flower, attracting by the fragrance of their blossoms a great number and variety of insects, more particularly Coleoptera.Many kinds of birds; parrots, toucans, and barbets, which live habitually in the forest, then visit the open places.
A few weeks of comparatively dry weather generally intervene in March, after a month or two of rain.The heaviest rains fall in April, May, and June; they come in a succession of showers, with sunny, gleamy weather in the intervals.June and July are the months when the leafy luxuriance of the campos, and the activity of life, are at their highest.Most birds have then completed their moulting, which extends over the period from February to May.The flowering shrubs are then mostly in bloom, and numberless kinds of Dipterous and Hymenopterous insects appear simultaneously with the flowers.This season might be considered the equivalent of summer in temperate climates, as the bursting forth of the foliage in February represents the spring; but under the equator there is not that simultaneous march in the annual life of animals and plants, which we see in high latitudes; some species, it is true, are dependent upon others in their periodical acts of life, and go hand-in-hand with them, but they are not all simultaneously and similarly affected by the physical changes of the seasons.
I will now give an account of some of my favourite collecting places in the neighbourhood of Santarem, incorporating with the description a few of the more interesting observations made on the Natural History of the localities.To the west of the town there was a pleasant path along the beach to a little bay, called Mapiri, about five miles within the mouth of the Tapajos.The road was practicable only in the dry season.The river at Santarem rises on the average about thirty feet, varying in different years about ten feet, so that in the four months from April to July, the water comes up to the edge of the marginal belt of wood already spoken of.This Mapiri excursion was most pleasant and profitable in the months from January to March, before the rains became too continuous.The sandy beach beyond the town is very irregular, in some places forming long spits on which, when the east wind is blowing, the waves break in a line of foam-- at others, receding to shape out quiet little bays and pools.
