THE TRAVELLERS
I have told in the last chapter how, on the ridges of Mont Ventoux, at
a height of nearly 6000 feet, I had one of those entomological
windfalls which would be rich in results if they occurred often enough
to serve the purpose of continuous study. Unfortunately, mine was a
solitary instance and I despair of ever repeating it. I can therefore
only base conjectures on it, in the hope that future observers will
replace my surmises with certainties.
Under the shelter of a broad, flat stone I discovered some hundreds of
Ammophilæ (A. hirsuta), heaped one on top of the other almost as
closely as the Bees in a swarm. As soon as I lifted the stone, all this
little hairy world began to run about, without making any attempt to
fly away. I shifted the mass by handfuls: not one of the Wasps looked
as though she wished to desert the rest. They seemed indissolubly
united by common interests; none of them would go unless all went. I
examined with every possible care the flat stone that sheltered them,
as well as the ground underneath and just around it, and discovered not
a thing to tell me the cause of this strange assemblage. Having nothing
better left to do, I tried to count them; and it was then that the
clouds came and put an end to my observations and plunged us into that
darkness of which I have described the anxious consequences. At the
first drops of rain, before leaving the spot, I hastened to put back
the stone and replace the Ammophilæ in their shelter. I give myself a
good mark, which I hope that the reader will confirm, for having taken
the precaution not to leave the poor insects whom my curiosity had
disturbed at the mercy of the downpour.
The Hairy Ammophila is not rare in the plains, but she is always found
singly by the side of the paths or on the sandy slopes, now engaged in
digging her well, anon busily carting her heavy caterpillar. She lives
alone, like the Languedocian Sphex; and it was a great surprise to me
to come upon such a number of this species collected under one and the
same stone almost at the top of Mont Ventoux. Instead of the isolated
specimen which I had known hitherto, a crowded company presented itself
to my eyes. Let us try to trace the probable causes of this
agglomeration.
The Hairy Ammophila is one of the very rare exceptions among the
Digger-wasps in the matter of nest-building; she gets hers ready in the
early days of spring. Towards the end of March, if the season be mild,
or at latest in the first fortnight of April, when the Crickets assume
the adult form and laboriously cast the skin of infancy on the
threshold of their homes, when the poet’s-narcissus puts forth its
first flowers and the Bunting utters his long-drawn call from the top
of the poplars in the fields, Ammophila hirsuta is at work digging a
home for her grubs and victualling it, whereas the other Ammophilæ and
the various Hunting Wasps in general postpone this labour until autumn,
during September and October. This early nidification, preceding by six
months the date adopted by the vast majority, at once suggests a few
reflections.
We wonder if the Ammophilæ whom we find occupied with their burrows in
the first days of April are really insects of that year, that is to
say, if these spring workers completed their metamorphosis and left
their cocoons during the previous three months. The general rule is for
the Digger to become a perfect insect, to quit her subterranean
dwelling and to busy herself with her larvæ all in one season. Most of
the Predatory Wasps leave the galleries where they lived as larvæ in
the months of June and July and display their talents as miners and
hunters in the following months of August, September and October.
Does a similar law apply to the Hairy Ammophila? Does the same season
witness the insect’s final transformation and its labours? It is very
doubtful, for the Wasp occupied on the work of the burrow at the end of
March would in that case have to complete her metamorphosis and to
break out of her cocoon during the winter, or at latest in February.
The severity of the climate at this period does not allow us to accept
such a conclusion. It is not at a time when the bleak mistral howls for
a fortnight without intermission and freezes the ground hard, it is not
at a time when snowstorms follow close upon that icy blast, that the
delicate transformations of the nymphosis are able to take place or the
insect to dream of abandoning the shelter of its cocoon. It needs the
warm moisture of the earth under the summer sun before it can leave its
cell.
If I knew the exact period at which the Hairy Ammophila emerges from
her native burrow, this would help me greatly; but, to my intense
regret, I do not know it. My notes, collected day by day, with the lack
of order inevitable in a type of research that is constantly subject to
the hazards of the unforeseen, are silent on this point, of which I
clearly perceive the importance now that I am trying to arrange my
materials in order to write these lines. I find the Sandy Ammophila
mentioned as hatching on the 5th of June and the Silvery Ammophila on
the 20th of that month; but my records contain not a word that relates
to the hatching of the Hairy Ammophila. It is a detail which, by an
oversight, has never been cleared up. The dates given for the other two
species come under the general law, which lays down that the perfect
insect shall appear during the hot season. I fix the same period, by
analogy, as that for the Hairy Ammophila’s emergence from the cocoon.
Then whence come the Ammophilæ whom we see working at their burrows at
the end of March and in April? We are driven to the conclusion that
these Wasps belong not to the present but to the previous year; that
they left their cells at the usual time, in June and July, got through
the winter and began to make their nests as soon as the spring came. In
a word, they are hibernating insects. And this conclusion is fully
borne out by experiment.
If we will but search patiently in the perpendicular banks of earth or
sand facing due south, especially those in which generations of
different honey-gathering Bees have succeeded one another year after
year and riddled the wall with a labyrinth of tunnels until it looks
like an enormous sponge, we are almost sure, in midwinter, to find the
Hairy Ammophila snugly ensconced in the shelters provided by the sunny
bank, alone or in groups of three or four, idly awaiting the arrival of
the fine weather. I have been able to give myself as often as I wished
this little treat of renewing my acquaintance, amid the gloom and cold
of winter, with the pretty Wasp who enlivens the greensward beside the
paths at the first notes of the Bunting and the Cricket. When there is
no wind and the sun is shining brightly, the warmth-loving insect comes
to its threshold to bask luxuriously in the hottest rays, or it will
even timidly venture outside and, step by step, stroll over the surface
of the spongy bank, polishing its wings as it goes. Even so does the
little Grey Lizard behave, when the sun once more begins to warm the
old wall that represents his native land.
But vain would be our search in winter, even in the most sheltered
refuges, for a Cerceris, Sphex, Philanthus, Bembex or other Wasp with
carnivorous grubs. All died after their autumnal labours and their race
is not represented, in the cold season, save by the larvæ slumbering in
their cells. It is, then, by a most rare exception that the Hairy
Ammophila, hatched in the hot season, spends the following winter in
some warm shelter; and this is the reason why she appears so very early
in the spring.
With these data to go upon, let us try to explain the cluster of
Ammophilæ which I observed on the ridges of Mont Ventoux. What could
these numerous Wasps have been doing, heaped up under their stone? Were
they preparing to take up their winter quarters there and, slumbering
under cover, to await the season favourable to their work? Everything
tends to show that this is improbable. It is not in August, at the
hottest time of year, that an animal is overcome with its winter
drowsiness. Nor is it any use to suggest the want of food, of honeyed
juices sucked from the flowers. The September showers are at hand; and
vegetation, suspended for a moment by the heat of the dog-days, will
gather fresh vigour and cover the fields with blossoms almost as
diverse as those of spring. This season of revelry for the majority of
Wasps and Bees could never be a period of torpor for the Hairy
Ammophila.
And then have we any right to imagine that the heights of Ventoux,
swept by the gusts of the mistral, which sometimes uproots both beech
and pine; that crests where the north wind sends the snow-flakes
whirling for six months in succession; that peaks wrapped for the best
part of the year in cold cloud-fogs, can be adopted as a winter refuge
by an insect enamoured of the sun? One might as well suggest that it
should hibernate among the ice-floes of the North Cape. No, it is not
here that the Hairy Ammophila can spend the cold season. The group
which I observed was only passing through. At the first hint of rain, a
hint that escaped us but could not escape the insect, which is so
highly sensitive to the atmospheric variations, the band of travellers
had taken shelter under a stone, waiting for the rain to stop before
resuming their flight. Whence did they come? Whither were they bent?
In this same month of August, and still more in September, we are
visited, in our warm, olive-clad regions, by caravans of little birds
of passage descending by easy stages from the countries where they have
wooed and loved, countries cooler, more thickly wooded, less wild than
ours, where they have reared their broods. They arrive almost on a
fixed day, in an unvarying order, as though guided by the dates of a
calendar known only to themselves. They sojourn for some time in our
plains, a halting-place rich in insects, which form the exclusive fare
of most of them; they ransack every clod in our fields, where the
ploughshare by now has laid bare in the furrows a multitude of grubs,
their special delight; thanks to this diet, they soon put on a fine
cushion of fat, a storehouse of reserve provisions for the coming
exertions; and at last, supplied with this viaticum, they continue
their southward flight, making for the winterless lands where insects
are never lacking: Spain, Southern Italy, the Mediterranean islands and
Africa. This is the season for brave sport with the gun and for dainty
roasts of small birds.
The first to arrive is the Shore-lark, or, as he is called in these
parts, the Crèou. August is hardly here before we see him exploring the
pebbly fields, in search of the little seeds of setaria, an ill weed
that overruns our tilled soil. At the least alarm he flies away with a
harsh clattering in his throat which is not badly represented by his
Provençal name. He is soon followed by the Whin-chat, who preys
placidly on small Weevils, Locusts, and Ants in the old lucern-fields.
With him begins the long line of small winged things, the glory of the
spit. It is continued, when September comes, by the most famous of
them, the Common Wheat-ear, or White-tail, extolled by all who are able
to appreciate his exalted qualities. No Beccafico of the Roman
epicures, immortalized in Martial’s epigrams, ever equalled the
exquisite, scented ball of fat that is the Wheat-ear, grown shamefully
stout on gluttonous living. He is an unbridled devourer of every kind
of insect. The notes which I have taken as a sportsman and naturalist
bear witness to the contents of his gizzard. It includes the whole
little world of the fallow fields: grubs and Weevils of every species,
Locusts, Tortoise-beetles, Golden Apple-beetles, Crickets, Earwigs,
Ants, Spiders, Wood-lice, Snails, Millipedes, and ever so many others.
And, as a change from this full-flavoured diet, there are grapes,
blackberries and dogberries. Such is the bill of fare for which the
Wheat-ear is ever in search, as he flies from clod to clod, with the
white feathers of his outspread tail giving him that fictitious look of
a Butterfly on the wing. And Heaven knows what prodigies of plumpness
he is able to achieve.
He has only one master in the art of self-fattening. This is one whose
migration synchronizes with his, one who is likewise an enthusiastic
insect-eater: the Bush-pipit, as the nomenclators so absurdly call him,
whereas the dullest of our shepherds never hesitates to speak of him as
the Grasset, the champion fat bird. The name in itself fully describes
his leading characteristic. No other achieves such a degree of obesity.
A moment comes when, laden with pads of fat up to its wings, its neck
and the back of its head, the bird looks like a little pat of butter.
The poor thing can hardly flutter from one mulberry-tree to the next,
where it stops to pant in the thick leafage, half choked with melting
fat, a martyr to its passion for Weevils.
October brings us the slender White Wagtail, half pearly grey, half
white, with a large black-velvet chest-protector. The graceful little
bird, trotting along and cocking up its tail, follows the ploughman
almost under the horses’ feet and picks the grubs in the new-turned
furrow. About the same time the Skylark arrives, first in little
companies sent out as scouting-parties, next in countless battalions,
which take possession of the cornfields and fallow land, with their
plentiful setaria-seeds, the bird’s usual fare. Then, in the plain,
amid the universal glitter of dewdrops and rime-crystals hanging from
every blade of grass, the treacherous mirror shoots forth its
intermittent flashes in the rays of the morning sun; then the little
Owl, released by the hunter’s hand, makes his short flight, alights,
starts up again convulsively, rolling frightened eyes; and the Lark
arrives, dipping on the wing, curious to obtain a closer view of the
bright apparatus or the grotesque bird. He is there, in front of you, a
dozen yards away, with feet pendant and wings outspread like the Dove
in a sacred picture. Now then: take aim and fire! I wish my readers the
excitement of this fascinating sport.
With the Skylark, often in the same companies, comes the Titlark,
commonly called the Sisi. Here again an onomatopœia gives us the bird’s
little call-note. None goes with greater fury for the Owl, round whom
he manœuvres and hovers constantly. But we will not continue the list
of the birds of passage that visit us. Most of them make but a short
halt here; they stay for a few weeks, attracted by the abundance of
food, especially of insects; then, plump and strong, they pursue their
southward journey. Others, fewer these, take up their winter quarters
in our plains, where snow is very rare and where thousands of little
seeds lie exposed on the ground, even in the depth of winter. One of
these is the Skylark, who gives his attention to the corn-fields and
fallows; another is the Titlark, who prefers the lucern-fields and
meadows.
The Skylark, so common in almost every part of France, does not nest in
the Vaucluse plains, where his place is taken by the Crested Lark, that
frequenter of the broad highway, the roadmender’s friend. But one need
not go far north to find the favourite spots for the Skylark’s broods:
the next department, the Drôme, is rich in his nests. It is very
probable therefore that, out of the numbers of Skylarks that come to
take possession of our plains for the whole of autumn and winter, there
are many that travel no farther than the Drôme. They have only to
migrate to the next department to find plains free from snow and a
steady supply of tiny seeds. A like migration to a short distance seems
to me to have caused the crowd of Ammophilæ which I surprised near the
top of Mont Ventoux. I have shown that this Wasp spends the winter in
the perfect insect state, hidden in some shelter and waiting until
April to make her nest. She also, like the Skylark, must take her
precautions against the frosty season. Though she need not fear the
lack of food, being capable of fasting until the return of the flowers,
she must at least, delicate creature that she is, guard against the
fatal attacks of the cold. She will therefore flee snowy country, the
districts where the ground freezes to a great depth; she will assemble
in a migratory caravan, after the manner of the birds, and, crossing
hill and dale, will select a home in old walls and sandy banks warmed
by the southern sun. Then, when the cold is past, all or part of the
troop will return to the place whence they came. This would explain the
Ventoux band of Ammophilæ. It was a travelling tribe which, coming from
the cold uplands of the Drôme and descending into the warm plains
beloved of the olive-tree, had crossed the wide, deep valley of the
Toulourenc and, when surprised by the rain, had called a halt on the
mountain-ridge. Apparently, therefore, the Hairy Ammophila has to
migrate in order to escape the cold of winter. At the time when the
little birds of passage start their procession of caravans, she too
journeys from a colder to a warmer neighbourhood. She has but to cross
a few valleys and a few mountains to find the climate which she wants.
I have two other instances of extraordinary gatherings of insects at
great heights. In October I have found the chapel at the summit of Mont
Ventoux covered with Coccinella septempunctata, the Seven-spot
Ladybird. The insects clinging to the stone of both the roof and walls
were packed so close together that the rude edifice looked, from a
little way off, like a piece of coral-work. I should not care to guess
the myriad numbers of the Ladybirds collected there. Those Aphis-eaters
had certainly not been attracted by the hope of food to the top of the
Ventoux, some 6000 feet above the level of the sea. Vegetation is too
scanty up there; and no Plant-louse ever ventured so high.
On another occasion, in June, on the tableland of Saint-Amans, a
neighbour of the Ventoux, at a height of 2400 feet, I witnessed a
similar gathering, only much less numerous. At the most prominent part
of the plateau, on the edge of a bluff of perpendicular rocks, stands a
cross with a pedestal of hewn stone. On each face of this pedestal and
on the rocks supporting it, the same Beetles, the Seven-spot Ladybirds
of the Ventoux, had gathered in their legions. The insects were mostly
stationary; but, wherever the sun beat at all fiercely, there was a
continual exchange between the newcomers, anxious to find room, and the
old occupants of the wayside cross, who took to their wings only to
return after a short flight.
Nothing here, any more than on the summit of the Ventoux, was able to
tell me the cause of these strange meetings on arid spots, containing
no Plant-lice and possessing no attraction for Ladybirds; nothing
suggested the secret of these crowded gatherings on masonry situated at
a great height. Were these again instances of entomological migration?
Were they general musterings, similar to that of the Swallows on the
day before their common departure? Were they meeting-places whence the
swarm of Ladybirds was to make for some district richer in edibles? It
is possible, but it is also very extraordinary. The Ladybird has rarely
been noted as a devotee of travel. She seems to us a very stay-at-home
creature when we see her butchering the Green-fly on our rose-trees and
the Black-fly on our beans; and yet, with her short wings, she holds
plenary assemblies, in immense numbers, on the summit of Mont Ventoux,
where the Martin himself ascends only at moments of violent energy. Why
these meetings at such altitudes? What can be the reason of this
predilection for blocks of masonry?