I got an urgent summons: “There’s a monstrous insect on the couch in the dining room, some kind of beetle, will you do something about it?”
It wasn’t a monster, it was a cockchafer and they’re insects I’m rather fond of so I carefully coaxed it into a glass tumbler, admired it for a few moments then released it outside.
Cockchafers can fly, although when you see their bulky bodies at rest this seems a little unlikely, but they’re not very good at it because they continually bump into things.
Their aeronautical attempts mostly take place at night in May and June. The weather had been warm and the diningroom has patio doors that had been left open for the evening. The cockchafer had obviously blundered in through them, they are attracted by lights in the same way that many moths are, and was taking a rest from the stressful business of being airborne on a comfortable couch.
They are large brown beetles, adults are 25mm to 3 mm long and stockily built, belonging to the scarab family. They are, or were, found across Europe but in the second half of the 20th century populations crashed and they became extinct in some areas. The cause of this was widespread use of agricultural insecticides. In the 1970s and 80s almost all these pesticides were banned in the EU because of fears that they posed a risk to human health. Since then, cockchafer populations have been slowly recovering.
Ireland was not as badly affected by the decline because we don’t have the same density of intensive arable agriculture and horticulture as other European countries.
The damage that cockchafers do is not done by the adult insects, which only live for five or six weeks and do no more than nibble at a few leaves. It’s the larvae which live underground and spend three or four years eating roots that farmers and vegetable growers dislike.
They are whitish grubs which look a little like caterpillars and can grow to finger length. Among the roots they eat are those of crops like potatoes and carrots. However, nowadays the only controls that can legally be used against them in the EU are biological ones such as parasitic nematode worms.
Because the larvae spend so long underground cockchafer populations tend to fluctuate and they are cyclically abundant every three or four years. There also seems to be a master cycle that results in an over-abundance every 30 to 40 years. One of these years of over-abundance appears to have been 1320 when the insects were brought to a court of law in Avignon and given three days to withdraw into a designated area. When they didn’t comply they were outlawed and killed. Ludicrous court cases like this were not unusual in the Middle Ages. The same court also put mice on trial for crimes against humanity.
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