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When you shouldn’t shave your legs

November 26, 2019

Insects catch prey by a variety of methods. Some like antlion larvae create traps by constructing funnels in the sand into which ants slide. Others like Scorpion Flies are ambush predators, hanging quietly from a piece of vegetation until an unsuspecting insect ventures too close. For some insects the capture of prey is a far more energetic activity.
 
Insects of the order Odonata i.e. dragonflies and damselflies (pictured below), and flies such as Robber Flies (pictured far below) catch prey on the wing. When prey flies through their territory they give chase and grasp the prey inflight with their legs. This requires excellent vision (these insects, see pictured, have enormous compound eyes), narrow wings for speedy flight, great flying dexterity and hairy legs!

 

Dragonflies, for example, can fly at speeds in excess of 50 kph. To stop prey slipping out of their grasp when hit at high speed, insects which aerially hunt have a collection of stiff hairs on their legs and claws as feet so that prey will not slip.

I guess the motto is No waxing or no food.

Here comes another sucker

November 24, 2019
by

Insects of the order Hemiptera, those that have sucking mouthparts, feature regularly in Focus on Fauna. These include cicadas, tree-hoppers, psyllids and scale. Well here’s another one.

Pictured below are the nymphs of a planthopper, so called because their defensive reaction is to jump free of danger. Adult planthoppers look like triangular spikes, often green in colour, on the stems of vegetation. In reality planthoppers are camouflaged by the shape and colour and move slowly to avoid detection.

Like all hemipterans the nymphs progress through several moulting stages until they finally become adult. Planthopper nymphs extrude a wax from the abdomen (picture) that aids in concealing  them from parasites or predators as the wax filaments can be spread out like a type of umbrella. It is also thought that because the nymphs do not have wings the filaments spread widely can act as a type of parachute if falling.

I had half a mind to call this blog Farting Fibre-optics.

 

… a snake’s belly

November 22, 2019

A grisly and sad sight confronted local farmer Terry while out on his tractor on the Broadford-Flowerdale Road. A Red-bellied Black Snake (Pseudechis porphyriacus) had been run over by a vehicle and the impact had dislodged its stomach content – an Eastern Brown Snake (Pseudonaja textilis). The brown snake was about 3/4 the length of the very fat black which was estimated at just under 1.5 metres long.

According to the Australian Museum, many Australian snakes eat other snakes as a normal part of their diet. The technical term for this is ophiophagy. True cannibalism – that is the eating of the same species – has also been observed in a number of snakes, including the two involved here. Many years ago we came across an Eastern Brown Snake with the tail end (1/2 a metre or so) of another of the same species trailing from its mouth. The half-coiled predator snake was shaking its head from side to side in an attempt to finish swallowing its victim.

The reverse of Terry’s encounter was experienced by Kay at Strath Creek back in 2014 when she watched, and recorded on video, an Eastern Brown Snake consuming a Red-bellied Black Snake. The dramatic video can be seen on a previous Focus on Fauna post Snake v snake.

There is still much to learn about snake diets, and chance observations like Terry’s, despite an unfortunate outcome, help to fill in the knowledge gaps. Citizen science at work!

It’s raining…beetles

November 20, 2019

During a recent bout of windy weather I was out walking Mac (the Border Collie) when a violent gust of wind caused a lot of debris to rain down from a tree I was walking under. The tree was an Elm of some sort and the debris was hundreds of beetles, Elm Leaf Beetles (Xanthogaleruca luteola), pictured left.

Originally from Europe these beetles were accidentally introduced to Australia. The adults and their larvae (pictured below) can cause serious damage to Elm trees by skeletonising old and emerging leaves. The result is rarely the death of the tree but the tree can be severely weakened and made vulnerable to diseases such as Dutch Elm disease.

As with many insect pests introduced into Australia, for example the European Wasp, in their native habitats cold winter temperatures kill off many of the insects thereby controlling the populations. However this does not happen in the milder Australian winters so the number of insects grows unchecked.

Unsurprisingly these beetles are of the same leaf-eating beetle family (Chrysomelidae) as the Eucalyptus Leaf Beetle in the previous blog.

It always amazes me how family members can look so different.

Excuse me. I thought you were a Ladybird

November 18, 2019

A combination of warming weather and fresh young eucalyptus leaves means the Eucalyptus Leaf Beetles (Chrysomelidae family) are not far away. These often highly coloured beetles are sometimes called Tortoise Beetles and are often mistaken for Ladybird Beetles because of their shape (pictured below). For those whose livelihood is growing plantation eucalypts the Tortoise Beetle is a pest as both the larvae and the adults eat foliage over a long period in the year.

The adults over-winter under bark or mulch and come out in late spring/early summer to mate. Eggs are laid on the young eucalypt leaves and the hatched larvae as a group consume the entire leaf before moving on to the next. Disturbing them produces a reaction similar to that of spitfires, the abdomen gets raised and a mixture of hydrogen cyanide and eucalyptus oil is emitted (pictured below left). Two generations of beetles can be produced each season.

The larvae prefer young leaves whilst the adults eat older leaves, leaving the characteristic half-moon shapes on the leaf margins.

Eucalyptus Leaf Beetles are small (larger than a Ladybird) and very common. You will inevitably find them if you look carefully at your gum trees this summer. They will be either eating or mating or in some cases the female will eat whilst the male mates (pictured right).

What a way to spend the summer.

Not following the rules

November 15, 2019

Everyone knows that spring is Magpie season. This is shorthand for watch out for them swooping as they defend their territory from anyone who passes through whether it be by walking, cycling or any other form of locomotion. As a cyclist myself I have several defence mechanisms. The first is the cable-ties sticking vertically out of the bike helmet. This does little to deter the attacking bird but does extend the safety buffer around your head so that you don’t lose a chunk of ear. I have also had success with gluing a pair of eyes (the facsimile thereof) on my helmet. Australian Magpies (Gymnorhina tibicen) tend not to swoop when being watched.

Yesterday however I was swooped by a Grey Butcherbird (Cracticus torquatus), pictured above. Grey Butcherbirds are of the same family as Magpies, Currawongs and Woodswallows. They are smaller than Magpies but occupy the same ecological niche. They feed on small vertebrates including other birds (and cyclists!)

The difference seems to be that Grey Butcherbirds don’t seem to care whether you are watching them or not when they swoop. I dismounted my bicycle and had many opportunities to try and photograph the incoming missile (right). It did not seem daunted at all by the fact I was facing it.

It obviously hasn’t read the rule book.

Neither cuckoo nor shrike

November 12, 2019

Black-faced Cuckoo-shrike

Following the previous post by Ronlit on unexpectedly finding water birds nesting high in trees, in the case of the Black-faced Cuckoo-shrike it is not unexpected at all for this arboreal bird, but what is surprising is that a) we managed to spot one high up in a large Yellow Box (Eucalyptus melliodora) right outside our front gate, and b) that cuckoo-shrikes ever manage to successfully breed since their nest is typically a small, shallow and flimsy affair precariously balanced in the fork of a branch and so is very susceptible to strong winds (and is very hard to see from below!).

Change-over time at nest duties

The Black-faced is the most widespread and common of the cuckoo-shrikes. It is migratory/nomadic, usually heading north in winter, but in 2010 it was recorded here in all months of the year. Both sexes share nest-building, incubation and feeding young.

White-winged Triller male


Another migratory bird in the cuckoo-shrike family (Campephagidae – meaning caterpillar-eater) is the White-winged Triller (pictured below) which is turning up in numbers in our district and, unusually, around southern Victoria, including Melbourne suburbs. The abundance of White-winged Trillers is known to fluctuate widely, and the last time we had a big influx of trillers was in 2013, when they could be heard in spring all around the Flowerdale/Strath Creek area.

Like all the cuckoo-shrike family, these two birds are unrelated to either cuckoos or shrikes. The origin of the name remains a mystery, though unconvincing explanations have been proposed about cuckoo-like plumage and flight, and shrike-like bill. As Fraser and Gray say in their book Australian Bird Names “… it is another awful combination of names of birds of entirely different orders…”.

To hear local recordings of the cuckoo-shrike and triller calls/song, click on the audio below.
Black-faced Cuckoo-shrike:

White-winged Triller: