A Slander! On the Colorado Beetle
Not only should we give the doryphore, the potato beetle, a feminine gender in French, as opposed to the masculine which seems more natural, indeed we should not call it by this name at all: the guilty party is properly a leptinotarsa. This is only the start of the hypocrisy and deceit of this insect, around which contempt has mounted up regarding a rather disreputable famine, although it eats the leaves of various plants but has no particular fondness for potatoes.
Since 1824, when the American Th. Say discovered the then anonymous creature when he was exploring the Rocky Mountains, the leptinotarsa had been known by various names (Colorado beetle, potato beetle, doryphora decemlineata); by 1870 it was habitually known as the doryphore, a name which proved to be incorrect on two counts when its true identity was discovered: leptinotarsa decemlineata. By this time it was too late, and the fact that its protective shell come to a point under its abdomen does not stop it continuing to be commonly known as a doryphore – a name which, in its masculine form in French, prompts thoughts of a Greek statue, an Australian tree, South American iguanas and frogs; a good word for crosswords!
We know that it was when potatoes began to be farmed that the evil instincts of this and many similar insects were triggered: when only wild potatoes were available to it, it was less prolific, or at least was not noticed.
Several times in a lifetime, each female lays around 1200 orange-coloured eggs. From the leaves on which they are laid, the eggs hatch into pink grubs, with black head and legs and two rows of black spots on the flanks; the grubs devour everything in their sight for three weeks before their chubby two-centimetre bodies climb down to the ground to turn into nymphs, and, 10 days later, into the mature insect – a sort of large ladybird, a centimetre and a half long, yellow in colour, with 5 black stripes along each elytron, under which hides a pair of very pretty red wings. Reproducing at a rate of three generations per year, females - although they generally die before this happens - would be grandmother to 600 x 600 x 1200 / 5 = around 33 million leptinotarsa, assuming that each batch of eggs contains as many males as females. We can easily see that a single female is enough to bring about the total destruction of several hectares of potato crops, in a space of two years.
The leptinotarsa family certainly seeks adventure. Already strong from the potato crops, it can also be quite self-disciplined and if need be make do with other solanaceae, eating tomatoes, aubergines, henbane, deadly nightshade, tobacco plants, and even petunias (and why not petunias?), even thistles in times of famine. It is resistant to heat and cold, burying underground in winter, and its only enemy is a ladybird with a real soft-spot for its eggs, the violent Virginia ladybird, which dispatches of it mercilessly. A bit of a joker, the ladybird appears to lay an egg on its head, and from this emerges a grub which then wriggles inside it through a gap in its protective shell and eats it alive. In 1861, the leptinotarsa appeared in Iowa; 10 years later, having crossed 3000 kilometres, laying waste to Missouri, Illinois, Indiana, Ohio, Pennsylvania, New York State and Massachusetts, it arrived on the shores of the Atlantic and set its sights on conquering Europe. It was difficult at the time to fly between the two continents: so it opted for sneaking in with export goods, packing straw, compost, all sorts of debris… The mortality rate was high, but the day the Weser Zeitung reported that a living specimen of the insect formerly known as the doryphore had been found in Bremen in a sack of corn on a liner from New York, the problem was solved. In 1877, leptinotarsa devoured their first field in Mulheim near Cologne. The field was immediately covered with sawdust, doused in oil and burned, then the soil was deep-ploughed and treated with quicklime. One month later, the neighbouring field struck back. A year later, 400 kilometres way, in Saxony…
Radical measures were taken by Europe against American potatoes. A law was passed in France in 1878 setting out the measures to be taken in case of an infestation: the insect disappeared.
It reappeared in England and Germany, where, about 18 years ago, troops were mobilised under the direction of engineers, to destroy, rationally and completely, the still limited threat. A mass programme of benzene to combat them was expensive, costing 20,000 marks per hectare.
When leptinotarsa are detected too late, when the surface area attacked is too varied in character and too large, or when they attack a country whose people still believe in shameful diseases, the only remaining means of defence are individual ones: drowning the insects in a mixture of water and oil, crushing batches of eggs, setting light to plants which have been attacked by the grubs, spraying pulped arsenic on leaves, disinfecting the soil with carbon disulfide, all procedures for which the Vegetation Protection Department can provide help and necessary equipment. Monsieur Saulnier, the head of this department, for whom a cultivation programme is not a cultivation programme unless it also includes a programme for cultivation protection, says: “This is a difficult struggle since we can only use macroscopic techniques against microscopic problems…” Clearly a single pair of leptinotarsa is enough to prevent the extinction of the species, and the resulting endemic state would not be very serious, the measures taken rapidly restrict the destruction, if there was not a ban on exports to England throughout the duration of the ‘leptinotarsia’. Logic demands that no boat from France should land on the English coast, as it would be enough for a single female to tread English soil, but probability calculus has, until now, meant that the ban has been limited to agricultural products. In any case, we should not always let ourselves be dazzled by what comes from the United States, or by the parasites carried by new populations. We have the old European cockchafer which is as good as any other and causes disasters far greater than the leptinotarsa has over the 10 years we’ve been fighting it. The phytophtoria fungus, for example, wreaks quite exemplary havoc.
So it’s not the end of the world. If, on top of all the measures taken, we also consider the invocations made to St Magnus and the plans to place them outside the law, there will be nothing left for the leptinotarsa to do but die out, or adapt to a diet of tax returns.
Jean Painlevé, 'Une calomnie, à propos de la leptinotarse' originally published in VU, n°201, 20 January 1932.