violet-like amidst clustering leaves, and even when showing itself still "half-hidden from the eye," was thereafter to be only a tantalizing image in memory. Still, my case was not so hopeless as that of the imagined lapidary; for however rare a species may be, and near to its final extinction, there must always be many individuals existing, and I was cheered by the thought that I might yet meet with one at some future time. And, even if this particular species was not to gladden my sight again, there were others, scores and hundreds more, and at any moment I might expect to see one shining, a living gem, on Nature's open extended palm.
Sometimes it has happened that an animal would have been overlooked or passed by with scant notice, to be forgotten, perhaps, but for some singular action or habit which has instantly given it a strange importance, and made its possession desirable.
I was once engaged in the arduous and monotonous task of driving a large number of sheep a distance of two hundred and fifty miles, in excessively hot weather, when sheep prefer standing still to travelling. Five or six gauchos were with me, and we were on the southern pampas of Buenos Ayres, near to a long precipitous stony sierra which rose to a height of five or six hundred feet above the plain. Who that has travelled for eighteen days on a dead level in a broiling sun can resist a hill? That sierra was more sublime to us than Conon-dagua, than Illimani.
Leaving the sheep, I rode to it with three of the men; aad after securing our horses on the lower
Seen And Lost. 373
slope, we began our laborious ascent. Now the gaucho when taken from his horse, on which he lives like a kind of parasite, is a very slow-moving creature, and I soon left my friends far behind. Coming to a place where ferns and flowering herbage grew thick, I began to hear all about me sounds of a character utterly unlike any natural sound I was acquainted with--innumerable low clear voices tinkling or pealing like minute sweet-toned, resonant bells--for the sounds were purely metallic and perfectly bell-like. I was completely ringed round with the mysterious music, and as I walked it rose and sank rhythmically, keeping time to my steps. I stood still, and immediately the sounds ceased. I took a step forwards, and again the fairy-bells were set ringing, as if at each step my foot touched a central meeting point of a thousand radiating threads, each thread attached to a peal of little bells hanging concealed among the herbage. I waited for my companions, and called their attention to the phenomenon, and to them also it was a thing strange and perplexing. "It is the bell-snake!" cried one excitedly. This is the rattle-snake; but although at that time I had no experience of this reptile, I knew that he was wrong. Yet how natural the mistake! The Spanish name of "bell-snake" had made him imagine that the whirring sound of the vibrating rattles, resembling muffled cicada music, is really bell-like in character. Eventually we discovered that the sound was made by grasshoppers; but they were seen only to be lost, for I could not capture one, so excessively shy and cunning had the perpetual ringing of their own
374 The Naturalist in La Plata.
little tocsins made them. And presently I had to return to my muttons; and afterwards there was no opportunity of revisiting the spot to observe so singular a habit again and collect specimens. It was a very slender grasshopper, about an inch and a half long, of a uniform, tawny, protective colour--the colour of an old dead leaf. It also possessed a protective habit common to most grasshoppers, of embracing a slender vertical stem with its four fine front legs, and moving cunningly round so as to keep the stem always in front of it to screen itself from sight. Only other grasshoppers are silent when alarmed, and the silence and masking action are related, and together prevent the insect from being detected. But this particular species, or race, or colony, living on the sides of the isolated sierra, had acquired a contrary habit, resembling a habit of gregarious birds and mammals. For this informing sound (unless it mimicked some warning-sound, as of a rattlesnake, which it didn't) could not possibly be beneficial to individuals living alone, as grasshoppers generally do, but, on the contrary, only detrimental; and such a habit was therefore purely for the public good, and could only have arisen in a species that always lived in communities.