Tuesday, 24 July 2018

A visit to the National Insect Collection CSIRO

The organiser of the Plant Science Group within the Friends of the Australian National Botanic Garden (Anne Campbell)arranged for the Group to visit the National Insect Collection maintained by CSIRO at their Black Mountain facility.  We were to be shown around by Ted Edwards and Marianne Horak, both of whom are retired lepidopterists at the Collection.  (They have retired from the payroll at CSIRO, not from study of moths!)

I'll start with a huge thank-you to all three of them for an extraordinarily interesting visit.  I hope I can remember enough of what we were told and shown to make sense in what follows!

We began with some big and pretty insects,  The blue ones and the green ones are the same species (with the females a brown colour).  This fits their lifestyles with the males living above the rainforest canopy and the females lurking below.If I have it correctly these are coloured by pigmentation.  The third case has moths with orange colours: this is due to the arrangement of the scales with in their wings.
Some moths have a mixture of the two methods of creating colours.  The yellow colour is a warning to predators that the species is poisonous.

In general members of the lepidoptera which fly by day (mainly butterflies, with more researchers than moths) rely on colour (ie vision) to attract mates while those that fly by night rely on pheromones (ie scent).  There was also a situation where one sense (I think scent) was used to get the pair together but the other sense (a grey element in the pattern)  provided confirmation

This set were shown to illustrate how the specimens are pegged out to dry.
This tray are cossid moths which have their larval and pupal stages in gum trees.  They are large!
Here is Ted holding a branch in which a cossid was lurking until a Yellow-tailed Black-Cockatoo happened along and heard the caterpillar moving inside.  It would take about 5 minutes to wreak that damage on a branch.
Another unfortunate experience for a cossid is if a braconid wasp came along.  They detect the larva by feeling the branch with their antennae and when a caterpillar is found inserting their long ovipositor through the wood into the larva.

These colourful jobbies can be identified as quite primitive as the fore and hind wings are similar in shape and don't overlap.  They are also unusual in that the male releases the pheromones.
This tray are Golden Sun Moths, which have delayed many slum developments in Canberra. I think they are also responsible in the mountains for clearing patches of snow grass.
Ted talked a far bit about the role of moths in breaking down leaf litter in ways that become natural fertiliser.  When a "controlled burn" removes all the litter it also removes the moths and more importantly most of the nitrogen and phosphorous fertiliser which the moths would feed back into the soil.

Some moths have been found to like their vegetable matter conveniently packaged in the easy to digest form of poop.  One species likes koala poop and another possum poop.

Ted finished his section with these huge Hercules Moths.  They can be regarded as the biggest  moth if size is assessed by wing area.  Other moths are bigger in terms of weight (although that can vary a lot depending on whether a female has just laid a mass of eggs!
Marianne then took over with discussion of Scribbly Gum moths.  Their research began serendipitously with the daughter of one of our group noticing something (several years ago) and being lucky enough to raise it with either Ted or someone else from the NIC.  They now know that the various patterns are made by different species of moth which tend to specialise in different species of eucalypt.  The current state of knowledge is described in this article.  Here are a couple of images cropped therefrom.

Of particular interest is the change in size of the trace.  This happens where the larva changes form and somehow stimulates the tree to form cambial cells (parenchyma) which the larva can digest rather than the very low-nutrition fibrous sclerenchyma making up most of the trunk of the tree.

A second point of interest is that the path of the larva stays within an area of bark which falls off as a plate.  There is currently no explanation of how this is recognised by the larva.  (Even without the larva the bark falls off as plates!)

The above does poor justice to the incredibly interesting issues raised by Ted and Marianne, but at least gets me to record something while it is somewhere near the surface of my brain

As I walked back to the car (parked at ANBG) I noticed this very spiffy plant, labelled as Pimelea physodes.  Its nothing to do with the talk but gets shown under the spiffy image rule.

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