Tuesday 3 January 2012

Sooty scale insect

St Arnaud, Nelson Lakes National Park, South Island, New Zealand

By lake Roititi you could not possibly have missed this remarkable scale insect. The females exude honeydew out of a very long hair like stalk and they had colonised many trees - the trunks looked rather hairy...
Southern beech trunk heavily infested with Ultracoelostoma spp.. Note a huge honeydew drop off the center.

Also there was a special sweet fermented scent by those trees. Their trunks were black because there is a black fungus that loves it, hence the name 'sooty scale insect'.

Honeydew drops against the light
I had heard that there was a scale insect associated with the southern beech trees but I had not seen it yet. So I was positively thrilled to see this and frantically busy with the camera trying to capture this remarkable phenomenon.
Let me explain what was going on. The scale insects feed on the sap and exude the extra sugars, the female does it in a very dramatic way from a stalk. Then this nutritious sugar feeds a lot of other animals: insects, birds and reptiles. I saw one weevil, some tiny moths and quite a few wasps. Now they were rather interesting to watch drinking the drops.
Common wasp Vespula vulgaris feeding on honeydew
There weren't that many wasps, it took me a while to capture one drinking. These wasps arrived in NZ uninvited and as later in the season they would be robbing the native wildlife of a very good food source something had to be done. So then they load traps with Fipronil, the workers take it to the nest where it kills the colony. Currently the traps weren't loaded.

Southern beeches are rather beautiful New Zealand trees. They belong to the genus Nothofagus, Family Fagaceae. This scale insect does not attack the silver beech N. menziesii, their trunks are silvery white.


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