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A Lesson in Light

February 9, 2019

The topic of beetles has been getting a bit of a flogging on this website lately.  At the moment they are out in force, feeding on nectar-bearing flowers. The Stag Beetle pictured left (Lamprima sp.) is one of these. It is stunning and its visual appearance is due to two different processes of light.

A close look at the carapace shows that it is dimpled. When the beetle is viewed from above in the sunlight it looks like it is covered in tiny little LEDs. This is due to reflection. The sunlight striking the beetle simply gets reflected back but at all different angles due to the curvature of the dimples.

The shimmering colours on the beetle’s shell (pictured above) are due to a process known as diffraction. Sunlight striking the shell gets broken up into spectral colours (nominally red, orange, yellow, green, blue, indigo and violet). Those old enough will remember the album cover of Pink Floyd’s Dark Side of the Moon showing light being diffracted into the different colours by a prism. This process is also responsible for phenomena such as rainbows, the blue bands on Blue-banded Bees and the colourful eye-spots on some butterflies and moths.

Instead of a prism diffracting the light on the beetle’s shell there are grooves. For these grooves to cause light diffraction they have to be spaced at intervals approximating the wavelengths of the colours. For example the wavelength of green light is nominally 550 nanometres (550 millionths of a millimetre) so the grooves must be similarly spaced, much smaller than the eye can detect.

So what makes this beetle so colourful is not only its cute dimples but its groovy shell.

Meet the parents

February 4, 2019
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The handsome creature pictured to the left is the larva of an antlion. The habits of antlion larvae were described in a blog five years ago (click HERE). They hunt by creating funnels in the sand. When an unsuspecting creature (usually an ant) slips down the slope of the funnel, the antlion larva waiting hidden at the bottom grabs the ant and drags it under the surface. It then immobilises the ant, injects it with enzymes and sucks out the juices. If you want to see one, locate the tell-tale funnel in a bare patch of sand and gently blow into it. The larva will be revealed at the bottom of the funnel. The parents though are much harder to find.

During the warm summer nights we usually leave our unscreened windows open. Last week an adult antlion (pictured right and below) appeared in our bathroom. Adult antlions look sort of like a dragonfly, sort of like a damselfly…sort of. Like damselflies, antlions fold their wings along their body (see below). But that is where the similarity ends. Antlions have long clubbed antennae whereas damselfly antennae are very short (click on photo far bottom left). In flight the antlion action is ‘fluttery’ compared to the direct motion of a damselfly.

Damselfly

Adult antlions are nocturnal, which is why we rarely see them. The fact that their lifespan is measured in weeks rather than months doesn’t help either. Depending on the species adult antlions eat nectar and pollen or small invertebrates.

Even though you’ve now met the parents it’s hard to see the family resemblance in the larvae.

Is the coast clear?

January 31, 2019

One of the dangers of watching and more-so writing about nature is that one can tend to anthropomorphise what we see  i.e. assign human characteristics and behaviours to the actions of animals. Doing so however can sometimes make a good story.

Our property is populated by Garden Skinks (Lamproholis sp.), pictured left. Watering the veggie patch results in a stampede of the little critters from underneath the straw mulch. We even have a few that slip in and out under the patio doors and live inside the house.

Skinks are one of the five broad groups of lizards, the others being Geckos, Legless Lizards, Goannas and Dragons. Only geckos have a larger number of species. Skinks are typified by a shiny, snake-like appearance and include not only Garden Skinks but also larger lizards such as Blue-tongues. In Australia there are 11 species of Garden Skinks. They are found in eastern and south-eastern Australia.

Garden Skinks feed on small invertebrates such as insects and spiders. The ones in our house patrol the window ledges for flies and other insects trapped in the house behind the glass. They also make a meal of the plentiful Daddy Long-legs (Pholcus sp.) who set up their webs in the same location hunting the same food.

Is the coast clear?

Last week whilst being entertained by one of our resident skinks devouring a fly, we noticed it stopped eating and raced to the window looking out. Sliding past was an Eastern Brown Snake (Pseudonaja textilis), pictured above right, another one of our reptile neighbours.

Now I might be anthropomorphising but tell me it’s not checking that the coast is clear.

Jewel of a spider

January 28, 2019

A common sight around our garden at present is the little spider pictured left. It’s a Jewel Spider, Austracantha minax, also commonly known as Spiny Spider or Christmas Spider (supposedly because it’s most numerous around Xmas time). It looks like a cake decorator has been busy with the icing bag on its back, and its underside is also colourfully patterned (see below, right).

The Jewel Spider belongs to the orb-weaver family Araneidae. It is the only member of the genus Austracantha and is endemic to Australia. All the ones we have found lately have been solitary, but it is common for them to hang out in groups, building extensive intertwining webs, presumably to improve the chances of prey capture, but proving a curse to bushwalkers.

The female (pictured) is larger than the male and spends her time sitting at the centre of her spiral web. Unlike some other orb-weavers, the web is relatively permanent and not rebuilt every day.

The Jewel Spider has an interesting ploy to improve the web’s durability – it adds white silk tufts at intervals along the main support and anchor threads (see web photos below) to increase their visibility to larger animals so they are less likely to go barrelling into the web.

The rest of the web is very fine and near invisible to the spider’s prey of small flying insects.

So keep an eye out for this little jewel, if only to avoid getting tangled in its web.

Hiding your colours

January 25, 2019

On these warm summer nights I have taken to walking Mac the dog late at night with a head-torch (that’s me wearing the torch not Mac ). It has revealed a wonderful world of critters, usually by having them slap you in the face as they swarm around the light.

One of the more striking moths seen recently, pictured left, sent me scurrying to the reference books to try and id it. It is a Fallen Bark Looper Moth (Gastrophora henricaria). The ‘looper’ term refers to the particular walking style of the caterpillar (see previous post).
 
 
The caterpillars feed on Eucalyptus and Brush Box (Lophostemon confertus) leaves. The Brush Box is a native of northern NSW / southern Queensland. Coincidentally a hitherto unknown bush on our property was, after 15 years, identified as a Brush Box earlier in the week (spooky!). It is currently flowering (pictured right) and is an absolute ‘wasp magnet’.

Macwake looked up the moth in Moths of Victoria Part 4 by Peter Marriott, and sent me the picture below from the accompanying CD. The moth in question is a male and its underwings are stunning.

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It’s a pity I didn’t know this at the time of taking the photo otherwise I would have poked it with a stick…only joking.

Life’s not easy at the Blue-banded B&B

January 21, 2019

The last blog described an external wall of our house where dozens of female Blue-banded Bees (Amegilla sp.) had made their nests by burrowing into the friable lime mortar. At the end of each burrow is a cell in which an egg and a food supply of pollen (for when the egg hatches) are sealed. Watching the bees come and go has been fascinating (better than the TV) but in doing so we have noticed a number of other insects loitering outside.

Black Spider Wasps (Fabriogenia sp.), pictured above left, have been searching all the nooks and crannies in the mortar to locate spiders which they detect by tapping their orange antennae on the surface. Once located the wasp immobilises the spider and takes it away to the nest where it lays eggs on it (see previous blog).

More troubling from a Blue-banded (BB) Bee point of view is the presence of Chequered Cuckoo Bees (Thyreus sp.), pictured right. Cuckoo bees do not build nests. Instead they wait until a Blue-banded Bee has just about finished loading the cell with pollen and then while the BB Bee is away they lay their own egg inside the cell. If the cuckoo bee larva hatches first it will eat all the food and the BB Bee larva will starve.

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Cuckoo bee (right) following a Blue-banded Bee (left) home

And if that wasn’t enough, Gasteruptiid Wasps (Gasteruption sp.) (pictured left) are also checking out the BB Bee nests when the bees are away. Adult wasps are nectar feeders and can be seen buzzing around flowers in summer. The female wasps of this type oviposit an egg into the BB Bee nest cell. When the wasp larva hatches it consumes the bee egg or larva and the stored pollen. This is called kleptoparasiticism.

They say that you can’t choose your family but you can choose who you mix with…unless they follow you home.

The blue-banded B&B is open for business

January 19, 2019

We have recently moved into an old brick building (ca. 1905) that is falling down. The very long list of repairs includes repointing all the lime mortar between the bricks which has weathered out over time. I also want to install a bee hotel (or B&B) somewhere in the garden. I have had several half-hearted attempts at this elsewhere but now it’s time to get serious.

My guru on bees and other things pollinating is Karen Retra, based in Albury. One of her many jobs is to coordinate the Wild Pollinator Count, a citizen science project run twice a year. Karen’s website contains some really great downloadable resources including how to build bee (& other critter) hotels.

Walking next to the building last night after a very hot day I heard the buzzing sound I recognized to be that of Blue-banded Bees (Amegilla sp.) (who’s calling me a nerd?). Looking up I saw not one or two but dozens of these bees coming back to their nesting sites in the weathered mortar (photos above and right).

Blue-banded Bees, covered previously on this blog-site, are native to Australia. They build solitary nests burrowed into limestone, dried river banks and, surprise, surprise, mortar between bricks. At the end of the tunnel is a cell which contains a single egg.

Welcome to the Blue-banded B&B

I’m now in a dilemma. I have just purchased scaffolding so that I can access the upper reaches of the brick wall to repoint all the cracks and holes in the mortar (see picture left). Currently the scaffolding has temporarily been transformed into a viewing platform of my newly discovered residents but I will eventually have to renovate the building … or maybe not?

I now find myself living in the largest bee hotel in the world. I wonder how much of the mortar damage the little buggers did themselves!