Findings: Decline in hairy caterpillars

The large hairy caterpillars beloved of children are disappearing from Britain's countryside, writes Steve Farrar.

Populations have halved, probably in response to the warmer, wetter winters experienced over the past 15 years.

A survey has plotted the decline of the once-common garden tiger moth, whose recorded numbers fell by about 60 per cent between 1968 and 1999.

Preliminary results from a follow-up survey on 13 other moth species that winter as large hairy caterpillars, including the ermine, drinker and magpie, suggest that most are undergoing similar population crashes.

The research has been carried out by members of the Rothamsted Insect Survey Light-trap Network and scientists at Rothamsted Research Laboratory in Hertfordshire.

Kelvin Conrad, an insect population ecologist at Rothamsted, said: "The future for many species of moth looks very bleak."

He said the cause of the decline was unclear, but one possibility was that warmer, wetter winters were enabling fungal infections to spread among the caterpillars.

Dr Conrad said the fall in numbers seemed to pre-date a decline in distribution, implying that the collapse was not exclusively driven by loss of habitat.

Two species - the lackey and the figure-of-eight moth - had been hit especially hard, with numbers falling by 90 per cent.

One species - the ruby tiger - was bucking the trend. Dr Conrad suggested that numbers of this moth were rising because it has two generations a year and benefits from the longer, warmer summers.

He said the decline in the population of cuckoos that ate hairy caterpillars may be linked to the moths' decline, but more research would be needed to confirm this.

The findings were revealed last week at a meeting on insect distribution organised by the Zoological Society of London.

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