Two spot ladybirds as indicators of intense local air pollution.

Abstract

MOST individuals of the two spot ladybird, Adalia bipunctata, may be designated as red with black spots, or as black with red spots. Although intermediate forms are found, they usually constitute less than 1% of the population in Britain. The most commonly occurring black forms are under the control of a single gene and are genetically dominant over the red forms1. In parts of continental Europe2 and in Britain3,4, the frequency of black is highest in industrial and other areas with much atmospheric pollution; up to 97% melanics are found in Liverpool and Glasgow. Multiple regression analysis suggests that there is an association of high melanic frequency with smoke, but not with sulphur dioxide5, this conclusion is supported by results from Birmingham, where melanic frequencies fell soon after the introduction of extensive smoke control areas, which had only a relatively small effect on sulphur dioxide levels6.