gh LADYBIRDS TURN BLACK LIVING IN TOWN

Researchers from the Institute of Common Genetics, Russian Academy of Sciences, have analyzed Russian and foreign materials collected for more than a century and have compared them with their own observations in towns and preserves in recent years. It has turned out that black mutants, melanists, are met particularly often in large industrial centers. In St. Petersburg, Yalta, Staffordshire, Marseilles, Yerevan, Tashkent and Vologda, the melanists' share exceeds 70%. The closer to the city the population inhabits the suburbs of St. Petersburg, the more black ladybirds it comprises. In St. Petersburg they make 87.5 percent, in Vsevolzhskoye - 75 percent, in Sestroretsk, Old Petergof, Lomonosov and Kronshtadt - aproximately half of the local populations. For comparison, in the town of Lodeynoye Pole melanists' share makes about six percent, and in Vyborg - ten percent, which is common for European part of Russia.

According to the researchers, the ladybird population "blakening" in towns allows to witness the rearrangement of their genetic system under the influence of anthropogenic factors. As a matter of fact, it has turned out that some populations, particularly those inhabiting the areas along the boarder of the natural habitat, have the genes, responsible for tolerance to the town environment, coherent with the black coloration genes. Correspondingly, the individuals - bearers of this gene have more opportunities to survive in town and provide posterity. This phenomenon was referred to as "industrial melanism". For example, in Yerevan, the share of black ladybirds in the town population skyrocketed from zero to two thirds since 1910 through 1985 when the town underwent extensive development. Nevertheless, industrial melanism does not necessarily always takes place. For example, the ladybirds inhabiting Stockholm, would not refuse the red coloration. Siberian populations do to turn black either.

According to foreign researchers' data, the reverse process also takes place - populations return to the standard coloration when the man-caused pressure decreases. That was observed by German entomologists in Potsdam.

Ladybirds flourish in contemporary towns. Their favorite food, plant-louses, willingly settle on the plants poisoned with exhaust gas, spilled petrol and lubricants, alkali contained in the asphalt, and industrial emissions. No wonder that biologists found the bulk of beetles and their larvae in the most contaminated trees and bushes along busy highways.

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