The Naturalist in Nicaragua Part 1

The Naturalist in Nicaragua.

by Thomas Belt.

INTRODUCTION.

In the "Life and Letters of Charles Darwin," edited by his son, Mr.

Francis Darwin (volume 3 page 188), the following pa.s.sage occurs:--

"In the spring of this year (1874) he read a book which gave him great pleasure, and of which he often spoke with admiration, "The Naturalist in Nicaragua," by the late Thomas Belt. Mr. Belt, whose untimely death may well be deplored by naturalists, was by profession an engineer, so that all his admirable observations in natural history, in Nicaragua and elsewhere, were the fruit of his leisure. The book is direct and vivid in style, and is full of description and suggestive discussions. With reference to it my father wrote to Sir J.D. Hooker: 'Belt I have read, and I am delighted that you like it so much; it appears to me the best of all natural history journals which have ever been published.'"

Now that the book so highly recommended by such an authority is about to be introduced to a public which has. .h.i.therto only known it by hearsay, it will be interesting to inquire into the reason of its appreciation by such men as Darwin and Hooker--and Lyell, Huxley, and Wallace, with other leaders of the scientific world of that day, might be quoted to the same effect--and to give some particulars of the author's short active life.

The Belts were an old family which had been established at Bossal in Yorkshire since the reign of Richard II. The main line died out some twenty years ago, but about the beginning of the eighteenth century a member of the family went to the Tyne to join the well-known ironworks of Crawley at Winlaton. He and his descendants remained with the firm for over a century, and he was the great-great-grandfather of the grandfather of Thomas Belt born at Newcastle-on-Tyne on November 27, 1832.

Thomas was the fourth child of a family of seven. His mother possessed a singularly sweet and beautiful disposition; his father, much given to hobbies, was stern and unbending, and he himself combined an almost womanly gentleness with a quiet determination that unflinchingly faced all obstacles. With a high sense of personal honour, una.s.suming and even-tempered, he was only roused to anger by acts of oppression or wanton cruelty. Then his indignation, though not loud, was very real, and he acted with a prompt.i.tude which would hardly have been expected from his usually placid demeanour. A story is told of how one day sitting at table he saw through the window a man belabouring a woman. Without saying a word, he rushed out, pinioned the offender by the elbows and, running him to the top of a steep slope in the street, gave him a kick which sent him flying down the declivity. The incident is recalled merely as an ill.u.s.tration of his practical way of dealing with difficulties which stood him in good stead in many an out-of-the-way corner of the world when contending with obstacles caused either by the perversity of man or the forces of nature. He never carried fire-arms even when travelling in the most unsettled districts, and his firm but conciliatory manner overcame opposition in a wonderful way. In ordinary life he was the kindest and most considerate of men, and his transparent sincerity made friends for him everywhere. Nor was he ever happier than when a.s.sisting others in those pursuits which occupied his own leisure.

The interesting question as to what led Belt to become a naturalist is difficult to answer. "Environment" nowadays accounts for much, but none of his brothers--and all the family had a similar bringing-up--showed any inclination for what with him became the ruling pa.s.sion of his life. And yet, in a wider sense, "environment"

had probably something to do with it. In the first half of the nineteenth century Newcastle could boast of a succession of field-naturalists unequalled in the country--Joshua Alder and Albany Hanc.o.c.k, who wrote the monograph on British nudibranchiate mollusca for the Ray Society; William Hutton and John Thornhill, botanists; W.C. Hewitson, Dr. D. Embleton, and John Hanc.o.c.k, zoologists; Thomas Athey and Richard Howse, palaeontologists--these, and others like them, were enthusiastically at work collecting, observing, recording, cla.s.sifying. Fresh discoveries were being made every day; what are now commonplace scientific truisms wore then all the charm of novelty; the secrets of nature were being unveiled, and modern science was entering upon an ever-extending kingdom.

Into all this scientific activity Belt was born, and from his earliest years it may be said of him, as in the well-known lines it was said of Aga.s.siz:--

"And he wandered away and away With Nature, the dear old nurse, Who sang to him night and day The rhymes of the universe."

"And whenever the way seemed long, Or his heart began to fail, She would sing a more wonderful song, Or tell a more marvellous tale."

"If happiness," he wrote in his twenty-second year, "consists in the number of pleasing emotions that occupy our mind--how true is it that the contemplation of nature, which always gives rise to these emotions, is one of the great sources of happiness."

The earliest instance which has been remembered of his fondness for animal life occurred when he was about three years old. He had been in the garden and came running to show his mother what he had found. Opening his carefully gathered up pinafore, out jumped two frogs--to the great dismay of the good lady, for frogs are first cousins to toads, the dire effects of whose glance and venom were known to every one.

He received the best education the town could give, and was fortunate in his schoolmasters--first Dr. J.C. Bruce of antiquarian fame, and then Mr. John Storey, second to none in his day as a north-country botanist.

Belt's father was much interested in horticulture; and, possessing some meteorological instruments, entrusted him, when only twelve years old, with the keeping of a set of observations which showed not only the barometric and thermometric readings twice a day, and the highest and lowest temperatures, but also the rainfall, the state of the sky, the form of the clouds, and the force and direction of the wind. The elaborately arranged columns, full of symbols and figures, look very quaint in the careful boyish handwriting, and must have absorbed much of his spare time.

Insects, however, had the greatest attraction for him. He writes in his journal: "I have made a great improvement in the study of entomology, to which I have an ardent attachment." And a little later: "I find I have not time to study so many things. I am afraid that I will not be able to carry on entomology and botany together; but entomology I will not give up." He had been studying "electricity, astronomy, botany, conchology, and geology." At the age of sixteen he wrote: "I feel a longing, a natural desire, to explore and understand the ways of science. I am ambitious of doing something that will deserve the praise or excite the admiration of mankind." When the praise and admiration came, no one could have been more indifferent to them than himself. Nature, his "nurse,"

had become his queen; and never was there a more devoted, whole-hearted subject, a more simple-minded follower of science for its own sake without any thought of the honour or glory that might accrue thereby.

On August 10, 1849, he records: "I have been thinking for the last few days about fixing on some subject or pursuit on which to devote my life, as it is of no use first starting one subject and then another, thus learning nothing. After giving it a good deal of consideration, I have determined on studying 'Natural History,' not confining myself to any one branch of that vast subject. As this is a subject on which I intend to devote my leisure hours during the greater part if not the whole of my lifetime, I consider it to be of the greatest importance that I should lay a good foundation for it. I therefore intend during the ensuing winter to study the English language and composition, so as to be able to describe objects and explain my sentiments with greater clearness and precision than I can at present." The last sentence ill.u.s.trates the systematic thoroughness of all his work which was one reason of his success.

Belt's "leisure hours" were soon more numerous than he had antic.i.p.ated when recording his determination to devote them to natural history. Already his health had shown signs of giving way, and presently there was a nervous break-down which necessitated his giving up all work and being out in the open air as much as possible. But what appeared to be probably the wrecking of his life provided the opportunity which might not otherwise have occurred of encouraging and developing his inborn love of nature. Becoming a member of the Tyneside Naturalists' Field Club, he interested himself greatly in the local fauna and flora, and formed very complete collections of the plants, insects, and sh.e.l.ls. His name occurs frequently in the "Transactions" of the Club as the recorder of species new to the district. His health gradually improved, but it was doubtful whether he would be able to bear the strain of any indoor occupation, for which indeed he felt an ever-increasing aversion.

It was the time of the discovery of gold in Australia, and after much discussion he and his elder brother joined the stream of adventurers and sailed in 1852 for Victoria. In this rough "school of mines" he acquired that insight into the building-up of the earth's crust and that practical knowledge of minerals which served him so well in after-life as a mining engineer. But although the whole colony was in the grip of the gold-fever, Belt retained the same quiet habits of observation which had marked him at home--for there, as to whatever part of the world his work subsequently called him, the engineer was always at heart a naturalist. He proved an excellent observer, and a certain speculative tendency led him to group his observations so as to bring out their full theoretical bearing.

Amid real hard work he found time to evolve a theory of whirlwinds and to speculate upon the soaring of birds. A companion has recorded in the following terms another matter which engaged much of his attention at this time: "The boldest of his speculations, and one of the soundest, as after-events proved, was his plan for crossing the Australian continent. He proposed, at the time the government expedition was mooted, to replace the costly plans of the government by the following scheme:--That he and his brother Anthony (who was unfortunately lost in the "Royal Charter") should be conveyed to the Gulf of Carpentaria, with about twenty pack-horses loaded with provisions and water; that an escort should protect them for some twenty miles from the coast, and that then the two voyagers only, with their pack-horses, should make their way to Cooper's Creek, the farthest known accessible point from the Victorian settled districts. Belt argued justly: 'If we fail, only two lives will be lost, but all chances are in our favour; we are provided with water and food more than ample to cover the distance we have to travel. Every step of our road carries us homeward and to safety. If we never find a drop of water on the road, our animals have enough to carry those who have to bear the whole journey to their goal, and as the animals succ.u.mb they will be shot or turned adrift.' The event showed Belt's sagacity. The unfortunate government expedition left Melbourne loaded with camp-followers and impedimenta, and by the time they reached a few stages beyond Cooper's Creek were well-nigh exhausted. Burke, the leader of the expedition, in desperation started with his two men, Wills and King, and bravely struck out for the Gulf of Carpentaria.

Through desert and fertile plains, not altogether dest.i.tute of water, they reached in safety the northern sh.o.r.e of Australia; but the energy, the courage, and the strength that took them this long, weary journey did not suffice to carry them back over double the distance to their camp. Brave hearts! they struggled on; but King only, and as a worn-out man, ever saw Cooper's Creek again. Belt's plan would have solved the problem without loss of life and at a tenth of the cost." He always regretted that he had not the means of carrying it out independently of government a.s.sistance.

After eight years in Australia Belt returned to England, married, and was successively manager of mining companies in Nova Scotia, North Wales, and Nicaragua, sandwiching in between these appointments a visit to Brazil to report upon some gold mines in the province of Maranham. In whatever part of the world his work took him he turned for rest and relaxation to the branches of natural science for which the locality offered the greatest opportunity.

In Nova Scotia he began those investigations into the cause and phenomena of the glacial period which were to be the study of the last years of his life, and to which he himself attached the greatest importance. In Wales he took up the question of the age of the rocks in the neighbourhood of Dolgelly, and after much study of their fossils proposed the now accepted cla.s.sification of the Lingula flags of the Lower Silurian system into the Maenturog flags and slates, the Festiniog flags, and the Dolgelly slates. The collecting of lepidoptera was his chief amus.e.m.e.nt in Brazil, where he made his first acquaintance with the teeming life of the torrid zone and laid the foundation for those observations on tropical nature which his longer stay in Nicaragua gave rise to, and which are recorded in this book.

After his return from Central America, his services were in great request as a consulting mining engineer, and the succeeding years of his life were spent in almost continual travel: over all parts of Great Britain, to North and South Russia, Siberia, the Kirghiz Steppes, Mexico, and the United States. It was on one of his annual visits to Colorado that he was seized with sudden sickness and died on September 21, 1878, at the early age of forty-five.

Thomas Belt was an accurate and intelligent observer possessed of the valuable faculty of wonder at whatever is new or strange or beautiful in nature, and the equally valuable habit of seeking a reason for all he saw. Having found or imagined one, he went on to make fresh observations, and sought out new facts to see how they accorded with his supposed cause of the phenomena. "The Naturalist in Nicaragua" has therefore a value and a charm quite independent of the particular district it describes. As a mere book of travel it is surpa.s.sed by scores of other works. The country and the people of Nicaragua are too much like other parts of tropical Spanish America, with their dull, lazy inhabitants, to possess any novelty. There is little in the book that can be called adventure, and still less of geographical discovery.

And yet, the many and highly diversified phases in which life presents itself in the tropics enabled the skilled naturalist to fill a volume with a series of episodes, experiences, and speculations of which the reader will never tire. His keen powers of observation and active intellect were applied to various branches of scientific inquiry with unflagging ardour; and he had the faculty of putting the results of these inquiries in a clear, direct form, rendered the more attractive by its simplicity and absence of any effort at fine writing. He does not obtrude his own personality, and, like all genuine men, he forgets "self" over his subject. Instead of informing us whether or not he received "the salary of an amba.s.sador and the treatment of a gentleman," he scatters before us, broadcast, facts interesting and novel, valuable hints for future research, and generalisations which amply repay a close study. Not alone the zoologist, the geologist, but the antiquarian, the ethnologist, the social philosopher, and the meteorologist will each find in these pages additions to his store of knowledge and abundant material for study.

With all this, the work is not a mere catalogue of dry facts: it is eminently a readable book, bringing vividly before us the various subjects with which it is concerned. Minutely accurate in his description of facts and bold in his reasoning upon them, Belt covered so much ground that some of his theories have not held their own; but others have stood the test of time and been absorbed into the world's stock of knowledge, while all bear witness to the singular grasp of his mind and have stimulated thought and observation--which is a great virtue in theories, be they true or false.

It has been already stated that Belt devoted the scanty leisure of his last years to the study of the glacial period, entering with zest into the consideration of its cause, the method of deposition of its beds, and the time-relationship of man to it--complex questions on which his imagination had full scope, and which, had his life been prolonged, his patient acc.u.mulation of evidence might have ultimately led him to suggest answers that would have been generally accepted by scientific men. But the cause of the remarkable change of climate during those late Tertiary and post-Tertiary times known as the glacial period is still without a completely satisfactory explanation. In Belt's day geologists were inclined to get over the difficulty of accounting for the phenomena by any feasible terrestrial change by explaining them as the result of cosmical causes, and Croll's theory of the increase of the eccentricity of the earth's...o...b..t was widely received among them.

Belt, on the other hand, held that the cold was due to an increase in the obliquity of the ecliptic. But these astronomical explanations have not met with much acceptance by physicists; and so chemists have been turned to by some geologists for support of the hypothesis of the variation in the amount of carbon dioxide in the air, or of other alterations in the atmosphere, while others have gone back to the idea of geographical changes. That considerable oscillations of the relative levels of land and sea took place during the Ice Age has been now clearly established, and the general result of the investigations favours Belt's opinion that the land during part of that period stood much higher than now over the northern regions of Europe and North America. It would, however, lead us too far away from the present book to enter into even a cursory examination of his views upon the glacial period, and those readers who desire to pursue the matter will find a.s.sistance for doing so in the bibliography at the end of this Introduction.

Of more immediate interest to us are the "observations on animals and plants in reference to the theory of evolution of living forms"

which the t.i.tle-page announces as a part of the narrative, and which indeed form the main portion of the work. Upon the publication of Darwin's "Origin of Species" in 1859, Belt had become an ardent evolutionist, and was henceforth always on the look-out for facts in support of the theories which had breathed such new life into biological studies. In Nicaragua he devoted special attention to those wonderful protective resemblances, especially among insects, which Bates had explained by his theory of "Mimicry;" and as the subject crops up again and again in this book, the non-scientific reader will find it helpful to have before him an outline of the expanded and completed theory--though he should be warned that some writers have been too much inclined to attribute to "mimicry" any accidental resemblance between two species. How far such accidental resemblances may be carried is probably well ill.u.s.trated by the bee, the spider, and the fly orchis of our own downs and copses.

"Mimicry" proper is often confused with "protective resemblance,"

and it will be advisable to begin with the consideration of the latter.

Concealment, while useful at times to all animals, is absolutely essential to some; and it is wonderful in what different ways it is attained. In cases of "cryptic resemblance to surroundings" the shape, colouration, or markings are such as to conceal an animal by rendering it difficult to distinguish from its immediate environment. In most cases the effect is PROTECTIVE; but in snakes, spiders, mantids, and other preying animals it is termed AGGRESSIVE, since it enables these animals to stalk their prey undetected. It is probable that this power, when possessed by a vertebrate animal, nearly always bears the double meaning, as in the green tree frog, where the colouration is protective so far as it provides concealment from snakes, which are particularly fond of these frogs, and aggressive in that it allows flies and other insects to approach without suspicion.

There may be either General Resemblance to surrounding objects or Special Resemblance to definite objects. The plain sandy colour of desert animals, the snow white of the inhabitants of the arctic regions, the inconspicuous hues of nocturnal animals, the stripes of the tiger and the zebra, the spots of the leopard and the giraffe have all a cryptic effect which at a very short distance renders the creatures invisible amid their natural surroundings.

Nor is it necessary in order to attain this invisibility that the colouring should be really dull and plain. It all depends upon the habitat. Mr. Wallace has described "a South American goatsucker which rests in the bright sunshine on little bare rocky islets in the upper Rio Negro where its unusually light colours so closely resemble those of the rock and sand that it can scarcely be detected till trodden upon." A little observation will supply large numbers of instances of such protective colouration.

It is, however, in the insect world that this principle of adaptation of animals to their environment is most fully and strikingly developed. "There are thousands of species of insects,"

says Mr. Wallace again, "which rest during the day clinging to the bark of dead or fallen trees; and the greater portion of these are delicately mottled with grey and brown tints, which though symmetrically disposed and infinitely varied, yet blend so completely with the usual colours of the bark, that at two or three feet distance they are quite undistinguishable."

In protective resemblances at their highest state of perfection the colouring is not constant but, as Professor Poulton puts it in his delightful book on "The Colours of Animals", "can be adjusted to harmonise with changes in the environment or to correspond with the differences between the environment of different individuals." The seasonal change of colour in northern animals is a well-known instance of the former, and the chameleon's alterations of hue of the latter.

Besides General Resemblance, in which the general effects of surrounding colours are reproduced, we have Special Resemblance, in which the appearance of a particular object is copied in shape and outline as well as in colour. Numerous instances will be found in this book, and a "Leaf Insect" and a "Moss Insect" are ill.u.s.trated.

But the cla.s.sic example is the b.u.t.terfly from the East Indies so graphically described by Mr. Wallace, Kallima paralekta, which always rests among dead or dry leaves and has itself leaf-like wings spotted over with specks to imitate the tiny fungi growths on the foliage it resembles. "It sits on a nearly upright twig, the wings fitting closely back to back, concealing the antennae and head, which are drawn up between their bases. The little tails of the hind wings touch the branch and form a perfect stalk to the leaf, which is supported in its place by the claws of the middle pair of feet which are slender and inconspicuous. The irregular outline of the wings gives exactly the perspective effect of a shrivelled leaf." The wonderful "stick insects" in like manner mimic the twigs of the trees among which they lurk. Nor need we go abroad in search of examples, for among our own insects are countless instances of marvellous resemblances to the inanimate or vegetable objects upon which they rest. One of the most interesting is that of the geometer caterpillars, which are very plentiful, and any one can observe them for himself even in a London garden. They support themselves for hours by means of their posterior legs, forming an angle of various degrees with the branch on which they are standing and looking for all the world like one of its twigs.

The long cylindrical body is kept stiff and immovable, with the separations of the segments scarcely visible, and its colour is obscure and similar to that of the bark of the tree. Kirby and Spence tell of a gardener mistaking one of these caterpillars for a dead twig, and starting back in great alarm when, on attempting to break it off, he found it was a living animal.

Sometimes concealment is secured by the aid of advent.i.tious objects. Many lepidopterous larvae live in cases made of the fragments of the substances upon which they feed; and certain sea-urchins cover themselves so completely with pebbles, sh.e.l.ls, and so forth, that one can see nothing but a heap of little stones.

Perhaps, however, the most interesting instance is the crab described by Mr. Bateson, which "takes a piece of weed in his two chelae and, neither s.n.a.t.c.hing nor biting it, deliberately tears it across, as a man tears paper with his hands. He then puts one end of it into his mouth, and after chewing it up, presumably to soften it, takes it out in the chelae and rubs it firmly on his head or legs until it is caught by the peculiar curved hairs which cover them. If the piece of weed is not caught by the hairs, the crab puts it back in his mouth and chews it up again. The whole proceeding is most human and purposeful."

There is another cla.s.s of colours in which not concealment but conspicuousness is the object aimed at. Such colours are borne by animals provided with formidable weapons of defence (the sting of the wasp, for example), or possessed of an unpleasant taste or offensive odour, and their foes come by experience to a.s.sociate this form of colouring with disagreeable qualities and avoid the animals so marked. Belt was the first to account, in this way, for the conspicuous colouration of the skunk; and it is now believed that startling colours and conspicuous att.i.tudes are intended to a.s.sist the education of enemies by enabling them to learn and remember the animals which are to be avoided. The explanation of warning colours was devised by Mr. Wallace to account for the brilliancy in the tints of certain caterpillars which birds find disagreeable, and the subject has been princ.i.p.ally studied by experiments upon such caterpillars. But examples of warning colours are recognised, among many others, in the contrasted black and yellow of wasps, bees, and hornets, the bright red, black, and yellow bands of the deadly coral snakes, and the brilliantly coloured frog of Santo Domingo which hops unconcernedly about in the daytime in his livery of red and blue--"for nothing will eat him he well doth know."

But--and here comes in the principle to which the term "mimicry" is now restricted--if warning colours are helpful to noxious animals, then defenceless animals acquiring these colours will share in the protection afforded by them. And so we find a deceptive similarity between animals occurring in the same district, but not closely related, in which the mimicked form is unpalatable or has an odour repulsive to birds and lizards. It must, of course, be understood that the mimicry is unconscious, the result, as in the cases of cryptic resemblance, having been brought about by natural selection--the less perfect the mimicry the more liable are the individuals to be attacked, and the less chance have they of reproducing their kind.

This imitation was first accounted for by Mr. Bates in the case of the Heliconidae, a group of showy, slow-flying abundant b.u.t.terflies possessing "a strong pungent semi-aromatic or medicinal odour which seems to pervade all the juices of their system." It does not follow, of course, that what seems to us a disagreeably smelling fluid should prove distasteful to the palate of a lizard or a bird.

But careful observation of the b.u.t.terflies convinced both Bates and Wallace that they were avoided, or at any rate not pursued, by birds and other creatures; and Belt found that they were rejected by his tame monkey which was very fond of other insects. So their conspicuous wings, with spots and patches of yellow, red, or white upon a black, blue or brown ground, may fairly be considered an example of warning colouration--though Mr. Thayer has with great ingenuity and ac.u.men endeavoured to show that the markings are effective for concealment and that their value as warning marks is doubtful. Now, says Mr. Beddard, "in the same situations as those in which the Heliconias are found there also occur, more rarely, specimens of b.u.t.terflies minutely resembling the Heliconias, but belonging to a perfectly distinct family--the Pieridae. They belong to the two genera Leptalis and Euterpe, consisting of numerous species, each of which shows a striking likeness to some one particular species of Heliconia. This likeness is not a mark of near affinity; it affects no important character, but only the shape and colouration of the wings."

The particular resemblance here described was the origin of the theory of Protective Mimicry, the conditions under which it occurs being, according to Mr. Wallace:

1. That the imitative species occur in the same area and occupy the same station as the imitated.

2. That the imitators are always the more defenceless.

3. That the imitators are also less numerous in individuals.

4. That the imitators differ from the bulk of their allies.

5. That the imitation, however minute, is external and visible only, never extending to internal characters or to such as do not affect the external appearance.