Bark life

by Richard Jones

Up to town today, and while waiting for the number 12 bendy bus, 12-year-old and I examine the trunk of a lime tree overhanging the stop.

Horse chestnut scale insects, Pulvinaria regalisUp to town today, and while waiting for the number 12 bendy bus, 12-year-old and I examine the trunk of a lime tree overhanging the stop. There's a whole ecosystem in just a few square feet of bark.

Most prominent are the white waxy remains of horse chestnut scale insects, Pulvinaria regalis (pictured above). These strange insects can be quite unsightly on the bark of infested trees. In this case they've flaked away, leaving pale dusky echoes.

'Pine' ladybird, Exochomus quadipustulatusThey've probably been mopped up by the larvae of the badly named 'pine' ladybird, Exochomus quadipustulatus (left), which specialises in eating scale insects on broad-leaf and conifer trees. They're present as grey, wart-like pupae, and are pock-marking the bark like some strange disease.

Scattered among them are the larvae of a micro-moth, probably one of the many Coleophora species. Only about 5mm long, they're hidden in a sock-like bag of silk covered in bits of debris and lichen, which camouflage the creatures against the bark.

Remains of aphid eaten by minute parasitoid 'wasp', PraonA white aphid proves to be a dead and empty shell, hollowed out by the minute parasitoid 'wasp', Praon. The wasp eats the tender insides of the aphid, leaving a dry, mummified skin (left). It then burrows out through the underside and spins a disk-shaped cocoon underneath its victim.

Ctesias serraNext is what looks like a tiny animated scrubbing brush; it's the larva of a beetle, Ctesias serra. Related to carpet beetles, it scavenges on bits of insects left by spiders that make their messy webs under loose bark on old trees. Its long bristles protect it from spider jaws.

After a few minutes of browsing the bark, the bus arrives and we leave the thriving Tilia metropolis in Barry Road for the throngs of Regent Street.

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Talkback: Bark life
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Gardeners' World Web User 29/08/2008 at 13:42

Reply to R. W. Gellatly. You probably have the brown or soft scale, Parthenolecanium corni. It usually doesn't do much harm, and because it's the same colour as the stems it is easily overlooked.

Gardeners' World Web User 16/08/2009 at 10:08

[...] There's a good picture on the BBC Gardeners' World blog which looks very similar to my photograph. Bark life | Wildlife | Gardening Blog | Talk | BBC Gardeners' World Thanks, [...]

Gardeners' World Web User 28/11/2011 at 18:37

the scale insects look really big to what we find on some of our shrubs or vines, but we are not troubled by them very much I'am pleased to say.