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Gumtree Scale sacs

Eriococcus coriaceus


A row of felty oval-shaped sacs on a eucalyptus tree branchlet. Each sac would have been about 2mm long with a dark patch at the upper part. These sacs were tended to by sugar ants (Camponotus nigriceps). Each sac is said to contain an adult female scale insect. She lays hundreds of eggs within the sac. The whole cycle of this scale insect is said to take upto 50 days.


These scale insects are found only on several species of Eucalytpus trees. They are native to Australia but have spread to New Zealand.


Crawlers (nymphs of the scale insect) hatch out of these eggs and spread over the tree - some get blown away and so, spread over a wide area. The insects suck a large amount of sap from the tree and excess sap is secreted as a sticky "honeydew" which attracts sugar ants. These sugar ants are interesting in their own right - they are known to protect some hemipterans because of the honeydew. Pic #2 shows a little black ladybird on a neighbouring leaf. This ladybird is said to feed on the gumtree scale- There are three species of insects in the spotting, their lives all interconnected making this spotting pretty complex but a perfect albeit small example of life on this planet ! Info on ant: Camponotus nigriceps Info on gumtree scale:Eriococcus coriaceus

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Leuba Ridgway
Leuba Ridgway 11 years ago

Thanks Martin. I've been working on these for hours today and I just realised that you and Mark have already covered these months ago !!-could have saved myself all the trouble...still it's good to do a bit of research. I agree the leaf beetles are out but this is the first "new" one for me.

MartinL 11 years ago

Wow, there's a LOT happening. Your second link gives the name of the ladybird beetle too. They can tuck their feet under their shell and its hard for the ants to bother them=) I've seen four species of leaf beetles already. Nice info.

Leuba Ridgway
Spotted by
Leuba Ridgway

3802, Victoria, Australia

Spotted on Sep 11, 2012
Submitted on Sep 13, 2012

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