In Poland, you can more and more often meet the native, once rare praying mantis or the “black bee”, considered extinct. There are also Mediterranean species such as the linden moth or the wall clay moth; and even non-European ones, e.g. boxwood windows – says Dr. Marek Michalski from the University of Lodz.
As a researcher from the Department of Experimental Zoology and Evolutionary Biology at the University of Lodz explains, the decline in the number and diversity of insects is called the “insectocalypse”. As a result of the general decline in biodiversity and environmental pollution, wild bees and other pollinating insects are dying. However, a phenomenon that arouses particular emotions are invasions of alien species.
– The ongoing warming of the climate causes species previously found in Southern Europe to migrate north in increasing numbers, reaching, among others, to Poland, and even overwinter here and reproduce effectively. The same phenomenon causes native species, but once found only locally, in particularly warm places, to quickly spread throughout the country, says Dr. Michalski.
He adds that the migration of insects is facilitated by human activity. Sometimes scientists intentionally introduce certain species to help fight plant pests or perform some other useful task. More often, however, when transporting various goods, we take along insect “stowaways”. Some of them can settle in a new place, which sometimes brings disastrous results.
The great return of the praying mantis and the “black bee”
Among our domestic insects that are currently on a significant expansion, the researcher mentions the common mantis Mantis religiosa. It is the only one of over 2,300 species of mantis found in Central Europe. This insect, until recently considered a rare and very local specimen, has over the last dozen or so years moved from its refuges in south-eastern Poland and reached as far as Suwałki and Olsztyn. Single individuals were also seen in Łódź, and in the nearby Przedborski Landscape Park, sites containing hundreds of cocoons with eggs were found. Adult mantises usually appear in the second half of summer. They are large, fly well, even at night, and are often observed on balconies and by street lamps.
The second domestic insect whose expansion is causing considerable interest is the violet beetle, Xylocopa violacea, commonly known as the “black bee”. This species was observed in single localities at the turn of the 19th and 20th centuries, but after World War II it was considered extinct in Poland. Meanwhile, since 2000, isolated reports of the occurrence of the purple tree beetle in southern Poland began to appear. Later, further reports appeared, from almost the entire country, except the north-eastern regions. This insect, which builds nests for its larvae in dry wood, feeds on the nectar of flowers often grown in gardens, such as sweet peas, scallops or sedum. Due to its very large size and characteristic coloring, it is very easy to observe.
Invasion of the linden tree
A thermophilic, Mediterranean insect that has been significantly increasing its range in Europe over the last few years is the linden beetle Oxycarenus lavaterae. It belongs to the order of Hemipterans. It resembles the popular blacksmith (called the “tramman”), but is smaller and less brightly colored. It is easy to notice because it forms huge clusters on linden trunks in the autumn and winter, especially on streets, even in city centers. This insect dies at temperatures below -15 degrees C, but a mild winter allows entire colonies to survive. Dr. Michalski emphasizes that so far it has not been found that the agglomerate causes major damage to trees.
The wall clay Sceliphron destilatorium, from the order of Hymenoptera, also comes from southern Europe. It is a large, brightly colored insect. Its females build large clay nests on the walls of buildings, and sometimes inside apartments, on furniture, curtains, etc. They bring spiders there, which are food for the larvae. A cop is basically harmless to humans, although it can sting weakly when threatened. It is sometimes confused with wasps and even hornets and is often killed.
Invasions of foreign – non-European – insect species include, among others: mass appearances of the small horse-chestnut butterfly Cameraria ohridella. At the same time, its cousins reached our country, feeding, among others, on linden trees, black locusts, plane trees and scarlet fireweed. Among the invasive insects that are currently on the rise, Dr. Michalski also mentions the so-called boxwood moth, professionally called Cydalima perspectalis. It was brought to Europe from East Asia along with boxwood seedlings, on which its caterpillars feed.
– This butterfly has an extremely short development time, up to 4 to 5 generations can develop per year. An additional factor facilitating the expansion of the boxwood fence in Europe is the complete lack of the so-called natural enemies – even insectivorous birds are not interested in its caterpillars – explains a scientist from the University of Lodz.
Another easy-to-see invasive insect that has been taking over Poland in recent years is the American plug, Leptoglossus occidentalis. This large, characteristic-looking bug feeds on pine trees, including trees planted in parks and gardens. In autumn, adult individuals, looking for places to spend the winter, also in the vicinity of human habitations, try to hide in apartments.
The researcher treats with caution the unconfirmed information about the discovery of the so-called tiger mosquito or Asian hornet. He emphasizes that real expansions and invasions of other insect species are taking place before our eyes. In his opinion, they are favored by increasingly mild winters and warm summers.