Changes over time in the proportion of the illustrated melanic and non-melanic morphs of the two-spot ladybird beetle along a transect of ca. 115 km in length in the Netherlands (bottom-left; source of map:
http://www.lesidee.nl/). Samples were collected in each of the 5 years indicated at 16 more or less evenly spaced localities from west to east. Colouring of years matches the histograms for melanic frequency in the individual samples from each locality. Trend curves were fitted by eye with those for 1995 and 1998 overlapping inland. Localities are (1) Ouddorp; (2) Goedereede; (3) Stellendam; (4) Dirksland; (5) Middelharnis; (6) Oude Tonge; (7) Achthuizen; (8) Ooltgensplaat; (9) Willemstad; (10) Klundert; (11) Zevenbergen; (12) Etten-Leur; (13) Oudenbosch; (14) Prinsenbeek; (15) Tilburg; (16) Waalre/Eindhoven. The smallest number of beetles in an individual sample was 35, with an overall mean of 818 (s.e.=288 and median=152). The panel on the bottom-right shows deviations in average temperature from a ‘normal’ season/year at De Bilt (red spot on map). From left to right, columns represent data for winter (Wi; December–February), spring (Sp; March–May), summer (Su; June–August), autumn (Au; September–November) and the overall year (Tot), respectively, and from top to bottom for different years beginning before the period of ladybird sampling. The colour of each block indicates the extent to which the average temperature in the particular season/year deviated from ‘normal’; white=no deviation, blue=cooler than normal (dark blue more extreme than light blue), red=warmer than normal (dark red more extreme than light red). For further details and the source of this panel see: http://www.knmi.nl/cms/content/71542/.