Thursday, 20 August 2009

Ladybirds play the villain

While it made a change from reading seemingly endless headlines about the credit crunch and the ‘will they, won’t they’ story of the ashes, recent coverage of the ladybird ‘invasion’ was nonetheless disheartening. In many ways it simply reinforced my view that we seem incapable of tolerating the natural world around us whenever it steps over the line beyond being simply a convenient backdrop to our daily lives.

The spectacle of many millions of 7-Spot Ladybirds concentrated along the coast of Norfolk should be something to marvel at, a mass of coleopteran life rarely seen in this country. Instead it was viewed as a threat, something that might keep the tourists away, curtail the summer and further deepen our economic gloom. Alarmist headlines, such as the Independent’s ‘Ladybird invasion hits Norfolk’, were matched by comments like ‘it was quite horrific’, ‘it ruined our visit’ and ‘there was absolutely no escape from them’. Still, at least we didn’t stoop to the levels seen in 1976 when far larger numbers were present, with cartoons showing ladybirds with teeth and, unbelievably, Nazi swastikas in place of spots. At worst, the presence of so many ladybirds was an inconvenience.

As was the case with the 1976 outbreak, the origins of the ladybirds involved this summer are somewhat unclear. Were they, as some have argued, immigrants blown in from the near Continent or were they home-grown ladybirds, the product of a good breeding season? I favour the latter explanation, in part because it follows the well-reasoned case made by the late Michael Majerus when explaining the origins of the 1976 occurrence. A successful breeding season last year, followed by a fairly mild winter and, importantly, a superabundance of aphids during the early part of the year would have enabled the 7-Spot Ladybird population to reach better than usual levels. A sudden decline in the aphid population, possibly weather-related, would have left the ladybirds devoid of a food supply, prompting them to move on. Those reaching the open sea would have turned back, to congregate on the coast where they covered boats, fence posts and other surfaces.

Look at photographs of these gatherings and you will notice that virtually every last individual is identical, such is the lack of variation seen in this particular species. This may seem like a fairly obvious statement, but many ladybird species show a great deal of variation in their appearance. Melanic forms are common and the number, shape and size of spots can vary considerably from one individual to another; counting spots will not necessarily help you to identify the species!  Rather than moan let’s celebrate a bumper year for this normally popular insect.

No comments:

Post a Comment