The GARDENA gardening expert
Dear Mr. F., your neighbours are quite correct: These are not beetles, but rather bugs. After winter hibernation in the soil, they appear at around this time in large groups and mate. They are then to be found on warm walls or at the foot of large trees (especially lime trees, horse chestnuts and robinias).
After mating (approximately 30 hours), they disappear again.
Red bugs look spectacular, but are almost completely harmless to humans and animals. However, it is better not to touch them, as they will react by excreting an acrid substance.
Don't squash or burn the poor things! They do not harm your garden.
They mainly feed on dropped plant seeds and dead insects, meaning that they are part of the “cleaning colony” in your garden.
Simply allow these ambassadors of spring a few days to mate; after that they will go away again. Where they are really not welcome, for example on a well-used paved path, simply brush up the red bugs very gently and carefully and carry them to the foot of a large tree, in particular the three varieties named above.