I have already told how on the top of Mont Ventoux, some 6000 feet
above the sea, I had one of those pieces of entomological good luck,
which would be fruitful indeed did they but occur often enough to allow
of continuous study. Unhappily mine is a unique observation, and I
despair of repeating it. Future observers must replace my probabilities
by certainties. I can only found conjectures on it.
Under the shelter of a large flat stone I discovered some hundreds of
Ammophila hirsuta, heaped in a mass almost as compact as a swarm of
bees. As soon as the stone was lifted all the small people began to
move about, but without any attempt to take wing. I moved whole
handfuls, but not one seemed inclined to leave the heap. Common
interests appeared to unite them indissolubly. Not one would go unless
all went. With all possible care I examined the flat stone which
sheltered them, as well as the soil and immediate neighbourhood, but
could discover no explanation of this strange assemblage. Finding
nothing better to do, I tried to count them, and then came the clouds
to end my observations and plunge us into that perplexing darkness I
have already described. At the first drops of rain I hastened to put
back the stone and replace the Ammophila people under shelter. I give
myself a good mark, as I hope the reader also will, for having taken
the precaution of not leaving the poor things, disturbed by my
curiosity, exposed to the downpour.
Ammophila hirsuta is not rare in the plain, but is always found singly
on the edge of a road or on sandy slopes, now digging a well, now
dragging a heavy prey. It is solitary, like Sphex occitanica, and I was
greatly surprised by finding such a number gathered under one stone at
the top of Mont Ventoux. Instead of my solitary acquaintance, here was
a great assembly. Let us try to educe the probable causes of this
agglomeration. By an exception very rare among mining Hymenoptera,
Ammophila hirsuta builds in the first days of spring. Toward the end of
March, if the season be mild, or at least in the first fortnight of
April, when the grasshoppers take their adult form, and painfully cast
off their first skin on their thresholds,—when Narcissus poeticus
expands its first flowers, and the bunting utters its long-drawn note
from the top of the poplars in the meadow,—Ammophila hirsuta sets to
work to hollow and provision a home for her larvæ, whereas other
species and the predatory Hymenoptera in general undertake this labour
only in autumn, during September and October. This very early
nidification, preceding by six months the date adopted by the immense
majority, at once suggests certain considerations. One asks if those
found burrowing so early in April are really insects of that year—i.e.
whether these spring workers completed their metamorphosis and came out
of their cocoons during the preceding three months. The general rule is
that the Fossor becomes a perfect insect, leaves its burrow, and
occupies itself with its larvæ all in one season. It is in June and
July that the greater part of the hunting Hymenoptera come from the
galleries where they lived as larvæ, and in August, September, and
October they follow their occupations as burrowers and hunters.
Does a similar law apply to Ammophila hirsuta? Does the same season
witness the final transformation and the labours of the insect? It is
very doubtful, for the Hymenoptera, occupied with mining at the end of
March, would have to complete their metamorphosis and break forth from
the cocoon in winter, or at latest in February. The severity of the
climate at that date forbids any such conclusion. It is not when the
bitter Mistral howls for a fortnight at a time and freezes the ground,
nor when snow-storms follow its icy breath, that the delicate
transformations of the nymph state can take place, and the perfect
insect venture to quit the shelter of its cocoon. It needs the soft
dampness of earth under a summer sun before it can leave its cell.
If I did but know the exact date at which Ammophila hirsuta leaves the
cocoon it would greatly help me; but, to my deep regret, I do not. My
notes, gathered day by day, show the confusion inseparable from
researches that are generally dealing with points that cannot be
foreseen, and are silent on this point, whose importance I fully
realise now that I want to arrange my materials in order to write these
lines. I find mention of the Ammophila of the sands coming out of the
egg on June 5, and A. argentata on the 20th; but I have nothing in my
archives regarding the hatching of A. hirsuta. It is a detail left
unnoticed through forgetfulness. The dates for the two other species
accord with the general law, the perfect insect appearing at the hot
time of year. By analogy I fix the same date for the coming forth of A.
hirsuta from the cocoon.
Whence, then, come those which one sees at work on their burrows at the
end of March and April? We must conclude that they were hatched in the
previous year and emerged from their cells at the usual time in June
and July, lived through the winter, and began to build as soon as
spring came. In a word, they are insects that hibernate. Experience
fully confirms this conclusion.
Do but search patiently in a vertical bank of earth or sand well
exposed to the sun, especially where generations of the various
honey-gathering Hymenoptera have followed one another year after year,
riddling the ground with a labyrinth of passages till it looks like a
huge sponge, you are nearly sure to see in the heart of winter A.
hirsuta either alone or in little parties of three or four, crouched in
some warm retreat, waiting inactive till summer shall come. This
cheering little meeting, amid the gloom and cold of winter, with the
graceful insect which at the first notes of the bunting and the cricket
enlivens the grassy paths, is one that I have been able to enjoy at
will. If the weather be calm and the sun has a little power, the chilly
insect comes out to bask on its threshold, luxuriating in the hottest
beams, or it will venture timidly outside and walk slowly over the
spongy bank, brushing its wings. So, too, does the little gray lizard,
when the sun begins to warm the old wall which is its home.
But vainly would one seek in winter, even in the most sheltered spots,
for a Cerceris, Sphex, Philanthus, Bembex, and other Hymenoptera with
carnivorous larvæ. All died after their autumn labours, and their race
is only represented by the larvæ benumbed down in their cells. Thus, by
a very rare exception, Ammophila hirsuta, hatched in the hot season,
passes the following winter in some warm refuge, and this is why it
appears so early in the year.
With these data let us try to explain the Ammophila swarm on the crest
of Mont Ventoux. What could these numerous Hymenoptera under their
sheltering stone have been about? Were they meaning to take up winter
quarters there and await under their flat stone, benumbed, the season
propitious to their labours? Everything points to the improbability of
this. It is not in August, at the time of the greatest heat, that an
animal is overcome with winter sleep. Want of their food—the honey
juice sucked from flowers—cannot be suggested. September showers will
soon come, and vegetation, suspended for a while by the heat of the dog
days, will assume new vigour and cover the fields with a flowery carpet
almost as varied as that of spring. This period—one of enjoyment for
most of the Hymenoptera—cannot possibly be one of torpor for A.
hirsuta. Again, can one suppose that the heights of Ventoux, swept by
the gusty Mistral, uprooting beech and pine,—summits where the bise
whirls about the snow for six months of the year,—crests wrapped for
the greater part of the year by cold clouds and mist,—can be adopted as
a winter refuge by such a sun-loving insect? One might as well make it
hibernate among the ice fields of the North Cape! No, it is not there
that A. hirsuta must pass the cold season. The group observed there
were making a temporary halt. At the first indication of rain, which,
though it escaped us, could not escape the insect so eminently
sensitive to the variations of the atmosphere, the wayfarers had taken
refuge under a stone, and were waiting for the rain to pass before they
resumed their flight. Whence came they? Where were they going?
In this same month of August, and especially in September, there come
to the warm olive region flocks of little migratory birds; descending
by stages from the lands where they have loved,—fresher, more wooded,
more peaceful lands than ours,—where they have brought up their broods.
They come almost to a day in an invariable order, as if guided by the
dates of an almanac known only to themselves. They sojourn for a while
in our plains, where abound the insects which are the chief food of
most of them; they visit every clod in our fields where the ploughshare
has turned up innumerable worms in the furrows, and feast on them, and
with this diet they speedily lay on fat,—a storehouse and reserve to
serve as nutrition against toils to come, and thus well provided for
the journey they go on southward, to reach winterless lands where
insects are always to be found, such as Spain and Southern Italy, the
isles of the Mediterranean and Africa. This is the season for the
pleasure of shooting and for succulent roasts of small birds.
The Calandrelle, or Crèou, as Provence calls it, is the first to
arrive. As soon as August has begun it may be seen exploring the stony
fields, seeking the seeds of the Setaria, an ill weed affecting
cultivated ground. At the least alarm it flies off, making a harsh
guttural sound sufficiently expressed by its Provençal name. It is soon
followed by the whinchat, which preys quietly on small weevils,
crickets, and ants in old fields of luzern. With the whinchat begins
the long line of small birds suitable for the spit. It is continued in
September by the most celebrated of them—the common wheat-ear,
glorified by all who are capable of appreciating its high qualities.
Never did the Beccafico of the Roman gourmet, immortalised in Martial’s
epigrams, rival the delicious, perfumed ball of fat the wheat-ear makes
when it has grown scandalously obese on an immoderate diet. It consumes
every kind of insect voraciously. My archives as a sportsman-naturalist
give a list of the contents of its gizzard. All the small people of the
fallows are in it,—larvæ and weevils of every kind, crickets,
chrysomelides, grasshoppers, cassidides, earwigs, ants, spiders,
hundred-legs, snails, wire-worms, and ever so many more. And as a
change from this spicy diet there are grapes, blackberries, and
cornel-berries. Such is the bill of fare sought incessantly by the
wheat-ear as it flutters from clod to clod, the white feathers of its
outspread tail giving it the look of a butterfly on the wing. Heaven
only knows to what amount of fat it can attain.
Only one other bird surpasses it in the art of fattening itself, and
that is its fellow emigrant,—another voracious devourer of insects,—the
bush pipit as it is absurdly styled by those who name birds, while the
dullest of our shepherds never hesitate to call it Le Grasset, i.e. the
fattest of the fat. The name is sufficient to point out its leading
characteristic. Never another bird attains such a degree of obesity. A
moment arrives when, loaded all over with fat, it becomes like a small
pat of butter. The unfortunate bird can hardly flutter from one
mulberry tree to another, panting in the thick foliage, half choked
with melting fat, a victim to his love of weevil.
October brings the slender gray wagtail, pied ash colour and white,
with a large black velvet gorget. The charming bird, running and
wagging its tail, follows the ploughman almost under the horses’ feet,
picking up insects in the newly turned furrow. About the same time
comes the lark,—first in little companies thrown out as scouts, then in
countless bands which take possession of cornfield and fallow, where
abounds their usual food, the seeds of the Setaria. Then on the plain,
amid the sparkle of dewdrops and frost crystals suspended to each blade
of grass, a mirror shoots intermittent flashes under the morning sun.
Then the little owl, driven from shelter by the sportsman, makes its
short flight, alights, stands upright with sudden starts and rolling of
alarmed eyes, and the lark comes with a dipping flight, anxious for a
close inspection of the bright thing or the odd bird. There it is, some
fifteen paces away—its feet hanging, its wings outspread like a
saint-esprit. The moment has come; aim and fire. I hope that my readers
may experience the emotions of this delightful sport.
With the lark, and often in the same flocks, comes the titlark—the
sisi—another word giving the bird’s little call. None rushes more
vehemently upon the owl, round and round which it circles and hovers
incessantly. This may suffice as a review of the birds which visit us.
Most of them make it only a halting-place, staying for a few weeks,
attracted by the abundance of food, especially of insects; then,
strengthened and plump, off they go. A few take up winter quarters in
our plains, where snow is very rare, and there are countless little
seeds to be picked up even in the heart of the cold season. The lark
which searches wheat fields and fallows is one; another is the titlark,
which prefers fields of luzern and meadows.
The skylark, so common in almost every part of France, does not nest in
the plains of Vaucluse, where it is replaced by the crested lark—friend
of the highway and of the road-mender. But it is not necessary to go
far north to find the favourite places for its broods; the next
department, the Drôme, is rich in its nests. Very probably, therefore,
among the flocks of larks which take possession of our plains for all
autumn and winter many come from no farther than the Drôme. They need
only migrate into the next department to find plains that know not
snow, and a certainty of little seeds.
A like migration to a short distance seems to me to have caused the
assemblage of Ammophila on the top of Mont Ventoux. I have proved that
this insect spends the winter in the perfect state, sheltering
somewhere and awaiting April to build its nest. Like the lark it must
take precautions against the cold season; though capable of fasting
till flowers return, the chilly thing must find protection against the
deadly attacks of the cold. It must flee snowy districts, where the
soil is deeply frozen, and, gathering in troops like migrant birds,
cross hill and dale to seek a home in old walls and banks warmed by a
southern sun. When the cold is gone, all or part of the band will
return whence they came. This would explain the assemblage on Mont
Ventoux. It was a migrant tribe, which, on its way from the cold land
of the Drôme to descend into the warm plains of the olive, had to cross
the deep, wide valley of the Toulourenc, and, surprised by the rain,
halted on the mountain top. Apparently A. hirsuta has to migrate to
escape winter cold. When the small migratory birds set out in flocks,
it too must journey from a cold district to a neighbouring one which is
warmer. Some valleys crossed, some mountains overpassed, and it finds
the climate sought.
I have two other instances of extraordinary insect gatherings at great
heights. I have seen the chapel on Mont Ventoux covered with
seven-spotted ladybirds, as they are popularly called. These insects
clung to the stone of walls and pavement so close together that the
rude building looked, at a few paces off, like an object made of coral
beads. I should not dare to say how many myriads were assembled there.
Certainly it was not food which had attracted these eaters of Aphidæ to
the top of Mont Ventoux, some 6000 feet high. Vegetation is too
scanty—never Aphis ventured up there.
Another time, in June, on the tableland of St. Amand, at a height of
734 mètres, I saw a similar gathering, only less numerous. At the most
projecting part of the tableland, on the edge of an escarpment of
perpendicular rocks, rises a cross with a pedestal of hewn stone. On
every side of this pedestal, and on the rocks serving as its base, the
very same beetle, the seven-spotted ladybird of Mont Ventoux, was
gathered in legions. They were mostly quite still, but wherever the
sunbeams struck there was a continuous exchange of place between the
newcomers, who wanted to find room, and those resting, who took wing
only to return after a short flight. Neither here any more than on the
top of Mont Ventoux was there anything to explain the cause of these
strange assemblages on arid spots without Aphidæ and noways attractive
to Coccinellidæ,—nothing which could suggest the secret of these
populous gatherings upon masonry standing at so great an elevation.
Have we here two examples of insect migration? Can there be a general
meeting such as swallows hold before the day of their common departure?
Were these rendezvous whence the cloud of ladybirds were to seek some
district richer in food? It may be so, but it is very extraordinary.
The ladybird has never been talked of for her love of travel. She seems
a home-loving creature enough when we see her slaying the green-fly on
rose trees, and black-fly on beans, and yet with her short wings she
mounts to the top of Ventoux and holds a general assembly where the
swallow herself only ascends in her wildest flights. Why these
gatherings at such heights? Why this liking for blocks of masonry?