Legging it
Butterflies are insects. That means they have three body segments – the head, thorax and abdomen. At a more detailed level the thorax is comprised of three body segments fused together. To each of these is attached a pair of legs. The abdomen is made up of 10 segments. Young butterflies i.e. caterpillars also have a three-segmented thorax and a 10 segment abdomen.
The caterpillar pictured above shows this typical structure. Even though they may seem to have more, caterpillars only have three pairs of legs. As in the adult they are attached to the three thoracic segments near the head (see picture above). What appear to be legs further down the body are known as prolegs. These are hydraulically powered appendages used for gripping plant stems
Butterfly and moth caterpillars have a maximum of 5 pairs of prolegs. They are positioned on segments 3-6 and (always) 10 on the abdomen. The caterpillar pictured above has two pairs of prolegs which are characteristic of moths of the Geometridae family. The Emperor Gum Moth caterpillar (Opodiphthera eucalypti), pictured left has the full complement of five pairs of prolegs.
The number of prolegs is diagnostic for insect type. The larvae of sawflies (e.g. spitfires) have between 12 and 16 prolegs in addition to the 6 true legs. Scorpionfly caterpillars top the list with 18 prolegs.
It’s lucky they don’t have to buy shoes.
Large scale discovery
A recent early spring-clean of my kitchen unearthed the desiccated body of an Imperial Jezebel (Delias harpalyce) butterfly under a shelving unit. Given that these are on the scene during summer my spring-clean was obviously not early enough. It was also an opportunity to have a closer look.
The Imperial Jezebel (pictured left) is one of the more colourful butterflies in the district and is endemic to Australia being distributed along the coast and ranges of NSW and Victoria. The eggs are laid on mistletoe plants with cocoons being formed in early autumn and the adults emerging in the spring.
As with all butterflies and moths the wings are flattened membranous sacs covered in scales (pictured right). The scales provide the butterfly with both protection against the elements and thermal regulation. Scales are attached to individual slots on the wing in overlapping transverse rows and are easily detached, particularly useful if caught in a spider’s web! Marginal scales on the wing edges are longer and form a fringing effect (pictured below left). In addition the male butterflies have sex scales that are associated with pheromone producing glands.
The Imperial Jezebel males and females have different coloured wings. Scale colours are either due to pigmentation in the scale or diffraction of light from minute structures on the scale surface. In addition to colour difference based on gender this butterfly has different colouration due to season, there being a summer form and a spring form.
A wardrobe of a grand scale.
The third eye (lid)
Most creatures have two eye lids. They serve the purposes of a. opening so as to allow vision, b. spreading tears across the cornea so that it remains moist, and c. closing quickly so as to protect the cornea from damage from debris.
Many creatures also have a third eye lid called a nictitating membrane, from the Latin word ‘nictare’ meaning to ‘blink’, that wipes horizontally across the cornea. It serves as a protective layer from dust and debris for creatures such as Blue-tongued Lizards (Tiliqua scincoides) pictured, that live close to the ground. For water creatures such as rakali, the Australian water rat, the membrane is draw across the eye when it is swimming underwater.
The nictitating membrane can be translucent when its main purpose is being a ‘windscreen wiper’ or transparent when its purpose is to protect the cornea from the outside environment such as under water or for animals e.g. Peregrine Falcon that travel at high speed. Birds, fish, reptiles and some mammals have nictitating membranes. In humans the structure in the corner of the eye known as the semilunar fold is a vestige of a nictitating membrane.
I could use some when I’m on my bike!
Just like Mum
EM keeps Giant Prickly Leaf Insects (Extatosoma tiaratum), pictured left. As pets they are pretty low maintenance. Once every few days you have to change the eucalyptus leaves on which they feed and in return you get just as much effort – very little. These insects are night creatures so when you get up in the morning they may have changed position on the gum foliage but during the day you’d be lucky to see a leg move.
They do however produce lots of droppings and lots of eggs that they unceremoniously drop on the bench. The job in the morning is to separate the eggs (pictured below) from the poo. What started off as three adult animals, one male and two much larger females has now dwindled to a single female. It still produces viable eggs though.
Leaf insects like many stick insects do not necessarily need a male and female parent to produce offspring. They can also reproduce by a process known as parthenogenesis (from the Greek parthenos meaning virgin and genesis meaning origin). An embryo can develop from an unfertilised egg. The offspring produced are female.
Last week a squeal of delight from EM heralded the arrival of the first offspring (pictured left). Given its parthenogenetic origin it is safe to say that it looks (or will look) just like Mum although measuring a mere 5mm in length it has a long way to go to match Mum’s 14cm size.
Looks like collecting gum leaves is on the agenda for quite a while yet.
Beware the destructor
Creatures of the phylum Arthropoda consist of fauna such as insects, spiders and centipedes, all regular subjects of this blog. They are all characterised by having a hard outer shell. Arthropods also include crustaceans such as crayfish. They are distinguished from others in the phylum by having two sets of antennae. The freshwater varieties in Australia are known by different names. Locally the smooth shelled crustaceans found in dams are called yabbies and are the species Cherax destructor.
Yabbies are highly adaptable tolerating a range of water quality and water temperature conditions. As a result their natural range is large extending throughout Victoria, through western NSW into Queensland.
In Flowerdale Ashton Fontana has been recently fishing yabbies out of their dam. These things are not small. Their current record is a ‘claw-tip to tail’ length of over 24 cm (pictured right). For those who want these crayfish in their dams beware. The species name is well founded given the amount of destruction they wreak burrowing into dam walls.
Be careful what you wish for.
Looking for a rodeo
Scarab Beetles make up a large family of beetles characterised by stout bodies and antennae that are clubbed or ‘fan-like’. This blog site has covered many of these beetles including Fiddler Beetles, Chafers and the summery Christmas Scarab.
Terry H has recently come across another scarab – the rather large Cowboy Beetle (Chondropyga dorsalis). This one has fan antennae that it uses to detect odours, and female beetles during mating season. The Cowboy Beetle is not considered dangerous or even a pest. Like most scarabs the adults are nectar feeders and the young feed on decaying wood.
These native beetles are found along the east coast of Australia.
Giddy up.
Make like a snake
In March 2021 I wrote a blog about very decorative caterpillars which turned out the larvae of Golden Notodontid Moths (Neola semiaurata) that I found munching down on the Black Wattles around the dam. The caterpillars themselves are fantastical to look at sporting many colours and imaginative plumes but what I didn’t realise at the time was their response to disturbance. When disturbed a bright red outgrowth called an osmeterium erupts from the throat and eye spots are displayed on the rear. I promised to give the caterpillar a tickle if I ever saw it again to check out these defensive strategies.
Moving on two years and the same Black Wattles are hosting the same caterpillars. Rather than ‘give it a tickle’ I could only go as far as slightly shaking the branch it was feeding on. It immediately went into its defensive posture (pictured above) that doesn’t look so scary when viewed from the side but when viewed from behind presents a far more daunting picture.
When disturbed the caterpillar arches its back over its body, squeezes its two rear ‘false legs’ together and reveals two large eye spots. Viewed from the rear it looks all-the-world like a small viper (pictured left). If I was a predator I’d be convinced to stay away.
As for the osmeterium – a more vigourous shake of the branch is obviously required.
A cross to bear
One of the most striking of the orb-weaver spiders is the St Andrew’s Cross Spider (Argiope keyserlingi) pictured left. It is distributed along the east coast of Australia. Although I have seen many photos of them I had never seen one until last week when I came across a hakea festooned with them.
Although when at rest the spider holds its legs in the shape of a St Andrew’s Cross it is named for the zig zag ribbons of silk it weaves into its web in the shape of that cross. In the picture below right the beginnings of the cross can be seen in the bottom left.
The reasons for the web decoration are not understood. One theory is that the silken cross is where the spider places its legs when on the web. Another theory proposes that the silken ribbon reflects extra UV light which is an attractant for insects. The cross could also be a device to make the web more obvious so that larger creatures such as birds don’t fly into it.
What we do know is that if we found a St George’s Cross Spider the web design will be a monochrome Union Jack.
No bees in here
It is summer. That means the Blue-banded Bees are in town and busily tunnelling into the lime mortar of the Butter Factory a.k.a. the Blue-banded B&B. Previous blogs have chronicled the comings and goings of these native bees and their attendant parasitoid entourage of cuckoo bees, cuckoo wasps and gasteruptid wasps.
Whilst sitting down for a coffee I noticed that a hairy insect (pictured) had wandered in from outside and across the carpet. Close examination showed that it was wingless and extremely hairy. It is because of the hair that this insect is known as a Velvet Ant (Bothriomutilla rugicollis). Velvet ant is the generic term for wasps of the family Mutillidae. As mentioned they are hairy, the male is winged and the female is wingless.
Adult velvet ants are nectar feeders however they are parasitoid in nature. After mating the female wasp searches for the nesting sites of ground-nesting bees and wasps. When it finds a nest it lays an egg near each host egg or larva. The velvet ant larvae hatch first and consume the host egg, larvae and/or food supply. These wasps are well equipped to survive the attention of predators. In addition to having an armour-plated exoskeleton, they have warning colourations, a warning sound and the female wasp has a potent sting.
The insect in question was obviously looking for the Blue-banded Bee nests but took a wrong turn and wandered inside.
Obviously better signage at the door is needed. Something like ‘Blue-banded Bees this way’ with an arrow.
Flight of the fledglings
I have never had kids but I imagine watching them drive off with their P-plates for the first time is a time of mixed emotions – pride and trepidation maybe. I experienced this recently watching two tiny Eastern Spinebills fly for the first time.
Eastern Spinebills (Acanthorhynchus tenuirostris) are a species of small honeyeater found in south-eastern Australia. In summer the female bird builds a nest and incubates the eggs for about two weeks after which time both parents feed the chicks. When the chicks are 2 weeks old they are ready to leave the nest.
This week two fledglings tried their luck at taking flight. Chick 1 (pictured left) displayed more ‘plummet’ than flight and with a furious flap of wings crash landed in the middle of the driveway. Chick 2 flew a bit further. Their incessant chirping combined with encouraging vocals from the nearby parents attracted the attention of the dog and the chickens who raced over for a look. To rescue them I placed both birds back in the nest but chick 2 launched itself in flight again with the same results. It was placed in the nearby tree (pictured below) out of harm’s way. For the rest of the afternoon I left them to it. Chick 2 I observed undertook little flights from branch to branch with the parents hovering nearby.
I prefer to let nature take its course. Normally my only intervention would be to maybe name them but I couldn’t let these two aviator-wannabes become chook food. I hope both chicks are now happily flying around my garden.
By the way I named them Wilbur and Orville.
Focus On Fauna 