Wednesday, 31 January 2018

January Moths on Black Mountain

This is a post to continue my partial coverage of the moths surveyed at Black Mountain. It is only a sample of the moths attracted to the lights set last week by Glenn (see previous monthly posts for details and comparisons). The little beauty above, was the first one I saw this time. It is a Pink Arhodia Arhodia lasiocamparia.

In profile, its colouring fitted well, striking, against the black night behind.

Yet on a substrate of peeling bark, its colouring did not seem so bold and in daylight would be difficult to spot. The caterpillars feed on gum eucalyptus leaves, of which Black Mountain has 800 ha, so they must be well fed. Wingspan 6-7 cm.

This was my favourite of the evening as I am always fascinated by how well animals can conceal themselves by shape, colour and posture against their background habitat's colour and form. In this case, leaf and bark litter on the forest floor. This is Antictena punctunculus.

Even the frayed hind edges of its wings blend in with the broken edges of the fallen leaves.
Wingspan 4 cm.

Not all the moths were attracted to land on the white illuminated sheet, many landed on nearby trees, especially the smooth-barked gums, like this specimen of a Cleora sp. This is a species of looper, so named because the caterpillars loop their body into a high arch when crawling. Wingspan 5 cm.

Then there was this late contender for favouritism, an Epicoma sp., possibly the male of the species below, Epicoma contristis. 

This was the Epicoma contristis female, she is silver while the males are darker, hence the reason why I think the former sample might be a male of this species. The caterpillars of this species are of the classic dark grey, bristling, hairy type. Wingspan 3cm.

The Epicoma have fantastic head 'hair' it completely covers their face. I don't know the purpose for this hair, and everything in nature has a purpose - thermoregulation in the cool Canberra nights? It is just so illuminating to discover what lives in the woods and how variable moths are in colour and form.

Another wonderful night on the mountain.

Saturday, 27 January 2018

Frogmouth Fledglings

two weeks and two months out of their nests

This pair of frogmouth fledglings have been out of their nest for two weeks, so as they were in the nest for four weeks, they are now six weeks old.

It is now January and most of the young frogmouths have left their nests, all those in my study areas have. When they do so, they become more obvious to people out walking and I am frequently asked how I can tell the age of the fledglings. So, here is a brief guide to the telling young and old frogmouths apart, using birds of known age.

This is the same pair seen in their family group. Mum is up top and dad is next to the chicks on the far right. He is slightly larger than the adult female and she has red on her wing coverts. Although the fledglings are well feathered, they are still only about half the adult size and weight.

The chick on the left is probably a male because it has grey coverts on its wings, the other one, in the middle, is probably a female as it has red/pink colouring on its coverts. Both can fly quite easily between trees as their wing and tail feathers are well developed, although their tails are not fully grown. Both chicks still have much fluffy down feathers around their heads and bellies, this is probably the best indicator that they are still young birds. The adults' body feathers lie smoothly against their bodies, except one stray feather on the male's upper wing which it is in the process of moulting out.

In a neighbouring territory, the fledglings have now been out of their nest for two months (so they are three months old) and they look much more like adult birds. In the above photo, the bird in the fore is a fledgling, that behind is its father. The bulges of stray downy feathers on the young bird's flanks catch the light as they stick up from the body. Those on the adult male lie flat and the under-tail coverts are longer and well streaked.

As most people view frogmouths from below, it is perhaps best to focus on what can be seen from below to guide aging these birds. And tails are the most obvious feature from that angle. The adult's tail on the left is long and smoothly edged. The youngster's tail on the right is shorter and ragged. The individual feathers are smooth, but they are of different lengths as they grow. When scrutinised, the young birds tail feathers look very smooth-tipped, the adult's tail fathers are usually frayed and chipped with wear as the bird has had most of them for a year or more. They will have pairs of fresher feathers within the mix as new ones are grown in replacement of those moulted out, but it is difficult to see that detail in the field.

In another month, they will be almost indistinguishable, but there are ways to tell.

Wednesday, 24 January 2018

Metamorphosing into chrysalides 

A Tailed Emperor Charaxes sempronius Caterpillar curls up in preparation for metamorphosing into a chrysalis - the final stage before it then metamorphoses into an adult butterfly. (See the previous posts for further details on my watch of these caterpillars)

I counted seven caterpillars on the host food plant, a Persian Silk Tree, and as I watching them over the days, I noticed that the first had disappeared a few days ago. So I traced the branches, looking for any wanderers. I first found one crawling swiftly along a branch, heading away from the leaves where it had grown, and probably where its egg had been laid. I measured its pace and was surprised that it was travelling at 20 m per hour. Not bad for a 6 cm long caterpillar. This is probably the most vulnerable stage in its life as it was exposed, with no camouflage while on the bare branches and predatory birds could easily spot it if I could. I found three, and one was still feeding, so where were the other three. Had they found a secluded spot or had they been eaten?

Once they had selected a suitable spot to settle, they fixed themselves by the a specialised hooked organ, called a cremaster at their tail end, to a silk pad they prepare on a branch. Then they hung down on it, and kept wriggling in a curled position to begin with.

Hours later, they let themselves go and hung down straight. This is when they begin to metamorphose.

However - all three of the ones I could find changed into their chrysalides overnight. I set up a slow-motion camera on two of them, but that only worked in daylight. By morning the chrysalides were almost fully formed. The shot above was taken late in the evening. The shot below, of the same animal, was taken next morning. The leaves of the tree close up at night and open by day.

The chrysalis forms inside the old skin of the caterpillar, and when ready, it breaks through the back of the skin. The old skin is then wriggled up to the tail end where it dries and is shaken off. All is complete. I shall now wait about two weeks and try to capture the emergence of one of the butterflies from a chrysalis in slow-motion time-lapse.

Wednesday, 17 January 2018

Tailed Emperor Caterpillars

As summer has warmed up and butterflies have become more abundant in the garden I have been watching for Tailed Emperor Charaxes sempronius females visiting or laying eggs on the Persian Silk Tree in the garden. I found a hatched butterfly there last year, so wanted to see any caterpillars.

See: the adult here

I haven't seen any butterflies yet this year, but at least one has laid eggs while I wasn't watching. I found chewed leaves the other day and I have been out at night watching the caterpillars since. They are mostly nocturnal feeders. Although I did see one feeding at about 1100 hr one day.

There are six of these caterpillars on the tree at the moment and they are all at this large stage. I never noticed any chewed leaves when they were small yellow instars.

There are many species of caterpillar which adopt defensive postures, curl up, or drop off their branch whenever they are approached by a potential predator, like me, but these didn't do that. They simply carried on eating or walking along a branch while I watched them. The four pairs of prolegs on the abdomen can be clearly seen in this photograph, with the pair of claspers on the last tail segment. The prolegs have tiny, tiny hooks on their tips for hanging onto vegetation.

Their heads are adorned with these marvelous horns. I watched an ant wander close to one and it faced it off, presenting its horned head-plate at the ant, tracing its path as it passed. Not that the ant probably noticed, they follow scents more than vision. But the horns might deter bird predators. And what are those two little horns in the centre. Anyone know?

In this photograph one pair of the true legs on the thorax can be clearly seen, they are segmented with little claws on the end. This caterpillar carried on munching as I clicked away, its mandibles chomping sideways at the leaf with quite astonishing speed and efficiency.

Once they have fed enough, they crawl back along their branches to pre-formed beds. These are silken pads spread on a leaf, or used to hold two or three leaves together. The silk is sticky, and firm on the leaf, and the caterpillars can hold onto it easily. This is important to help the caterpillars stay attached to the leaf when the wind blows. For they certainly bounced about one windy day when I was watching them. They held on effortlessly.

And there they sleep and grow for much of the rest of the night and most of the day, curled up safely camouflaged and with a firm grip of their leaf bed. Isn't it amazing what goes on in the garden.

Monday, 1 January 2018

Wet Scales

First day of the year and a grand day.

I went to Tidbinbilla Nature Reserve outside Canberra to wander around the wetlands. Well, specifically to see platypus as they are such gorgeous animals. That was as good as ever, so then on for a general look around and experience the wildlife.

While scanning the water surface of the ponds, I noticed a little ripple crossing from bank to bank. It was far too small for a platypus wake. It was a little lizard, about 15 cm long, a species of skink I have yet to identify - anyone know?

The lizard swam with a serpentine motion, waving from side to side with its legs tucked into its flanks, not used to paddle.

Farther on I saw another scaly creature in the water, a Red-bellied Black Snake. A beautiful snake and a marvelously adapted predator. This one was creeping up on another small lizard which was basking on the bank. It never got near enough to strike, or perhaps it did not really want to catch the lizard. That snake carried on slowly patrolling along the edge of the water. Then I noticed two more snakes within ten metres of the first. So I moved slowly and grabbed some shots.

Red-bellies are elapid snakes so are venomous, but they not aggressive and I only watched them, not approached them. They approached me while I kept still.

The red scales on their underside are a rich, yet delicate fiery colour. Their scales are always clean and they shone in the sunshine as the snakes slipped through the grass.

The detailed pattern of how the snakes' scales fit with one another is fascinating, exquisite and no more so than around the head.

They constantly flicked their forked tongues out when hunting, scanning the air for chemical clues of where prey might be lurking.

When seen head on, a victim's last view, they always impress me with their focused attention.