A stroll around the Palmetum

The Palmetum is one ‘campus’ of Townsville’s botanic gardens. Its special focus is palm trees, as its name implies, but palms range across so many habitats, from rainforest to desert, that the gardens are very varied. I found lots of wildlife to photograph on a Saturday afternoon stroll, even well into the Dry season.

grey honeyeater
Little Friarbird, Philemon citreogularis.

There were plenty of birds – Rainbow Lorikeets, Ibis, Black Duck and a few other familiar species, plus one which I had to look up. My first thought that it was a honeyeater, since it was about the size of our Blue-faced Honeyeaters and had a similar patch of bare skin on its face, but it turned out to be a Little Friarbird. I hadn’t been far wrong, however, since friarbirds are members of the same family (Meliphagidae) as honeyeaters.

But insects claimed most of my attention, although numbers were down in the park just as they are at home. I found a peculiarly-equipped bug,  several species of orb-weaving spiders, damselflies around the lagoon and in the rainforest, a few dragonflies and a few butterflies.

two brown butterflies on a leaf
Getting acquainted? Two Orange Bush-brown butterflies, Mycalesis terminus.

These butterflies are seen year-round but their colours, like those of other leaf-mimics,  depend on the season. Melanitis leda, the Evening Brown, is my favourite example of how they change – look at this collection.

Shape-shifting bug

Hopper adult and nymph
Leaf-hopper (Flatidae) adult and nymph

This picture could well have appeared in my gallery of microfauna a few days ago but I thought it deserved a little more prominence.

What do we have? Two insects on a plant stem, obviously. Two completely unrelated insects, most of us would think – like a man and his dog leaning against opposite sides of a lamp-post, for instance – but we would be wrong: they are the same species. The one on the right is a juvenile – a nymph – of the larger winged insect on the left.

They are Hemiptera – ‘true bugs’. The adults are known as leaf-hoppers or plant-hoppers and these two are probably Colgar rufostigmatum or Colgaroides acuminata in the family Flatidae. The nymphs, as far as I can tell, are not known as anything at all. They are only about 5mm long without the peculiar tail of waxy filaments and are easily overlooked. The adults are more visible, at 8mm or so, but can easily be mistaken for a spine or new leaf on the stem of the plant. Like many Hemiptera, they feed exclusively on sap they suck from the plant.

Insects of many families undergo radical transformations during their life cycle, of course. The caterpillar-pupa-butterfly sequence is well known (but still amazing); cicadas spend their long childhood underground, eating roots, and dig their way out to split open and take wing; dragonflies spend their infancy as ugly aquatic predators before climbing out and emerging as adults; and so on. By comparison mammals (like us) are boring  …  just about all we do is get bigger.

A superfluidity of cicadas

If you read my title carefully you probably thought I had made a mistake but no, it was deliberate – an attempt to capture this effect:

Cicada rain
Cicadas, some of them highlighted with boxes, showering the ground beneath their tree

I mentioned recently that our cicada season has started. We don’t have very many in our own garden but I visited a neglected garden on Hervey’s Range yesterday and was surprised to find the ground beneath one particular tree looked as wet as though a sprinkler had been on (and I knew it hadn’t). Looking up, I saw and felt a steady shower misting down from above, and spotted the cicadas responsible. Here’s a closer view:

Cicadas clustered on a branch
Cicadas clustered on a branch

There were hundreds, if not thousands, on this one tree (hardly any on nearby trees of different species), all sucking the sap for its nutrition and excreting the watery waste. If this goes on too long, the tree may not survive.

A ‘collective noun’ is the name for a group of animals – a ‘flock’ of sheep, etc. It seems that there isn’t one for cicadas, and I doubt that ‘superfluidity’ will catch on. We need one which highlights the most obvious characteristic of a big group, and that is surely the noise. I thought of a ‘clamour’ but that is already taken, by rooks. Other people (I looked on the net) have suggested a ‘chirrup’ or a ‘twitter’ but those are far too weak, too genteel, so I will propose a ‘scream’ or a ‘shrill’ of cicadas. This lot earned both of them, as well as a ‘superfluity’ and ‘fluidity’.

Mother love

Mother love is something we take for granted among ourselves but it is not universal in the animal kingdom, and nor is it easy to predict which kinds of animals will look after their young and which won’t. Most mammals, from whales to humans to mice, do; most birds do; most reptiles don’t, but crocodiles do; most spiders don’t but some, e.g. the Wolf spider, carry their babies around on their backs (see, too, Mummy Long-legs); and most insects apart from the social insects (ants, wasps, bees and termites) don’t.

Shield bug sitting over eggs
Shield bug sitting over eggs (click for larger view, as usual)

Parental care has been seen in only a few hundred non-social insect species out of about 20 million. Some of our shield bugs are in that minority. About a year ago I photographed an adult on a fern frond and only noticed the smooth whitish shape of an egg beneath … her, I realised … after I saw the image on screen. She was just under the edge of my carport so I went out next morning and saw the neat array of eggs nestled between her hind legs.

Seeing her guarding the eggs like that was a surprise but, even more surprisingly, she stayed with the eggs until they hatched a week later and with the nymphs (babies) for another few days yet. The eggs hatched on a Saturday, and mother and babies stayed together in the same spot until the Tuesday afternoon. Then Mum left, and the babies gradually dispersed over the next day or two.

Shield bug sitting over nymphs
After the hatching

That was at the end of July last year but it was not an isolated incident. I was reminded of it when I saw another mother standing protectively over her babies in August this year, and there are similar examples on Flickr’s Field Guide to Insects of Australia group and here on the Brisbane Insects site.

Interestingly, all of them feature the species in my photographs or a close relation, Poecilometis sp. (Hemiptera, Pentatomidae). They don’t appear to have any common name more specific than ‘stink bug’ (for the foul-smelling liquid they exude in defence) or ‘shield bug’ (for their shape).

The colourful Harlequin Hibiscus Bug (not my photo) is the only other Australian sap-sucker I know to show any care for its progeny. The mother will guard the eggs, but I don’t know whether she stays with the nymphs after they hatch.

Nymphs and eggshells
Nymphs and eggshells

Searching Flickr for ‘Hemiptera’ plus ‘eggs’ will find you many more pictures of adult insects (worldwide) with eggs but it is not always clear whether they are just laying them or protecting them afterwards.

A slightly shorter version of this post appeared in Kapok, newsletter of Coastal Dry Tropics Landcare, Inc., in September 2011.

What’s around – mid September

Shield Bug on trunk of paperbark tree
Shield Bug on trunk of paperbark tree - quite well camouflaged, but he won't get any sap out of it!

Still no rain to speak of, in spite of indications to the contrary, so there is little change in the insect life except a continued dwindling of numbers. The garden is presently dominated by wasps and flies – hover-flies are doing particularly well, and we have more orange-and-black Plecia flies than I have ever seen before – while spiders are almost absent; there are no Silver Orb-weavers or St Andrew’s Cross spiders and even the spiky Austracantha have almost vanished.

Looking for butterflies I see (still) plenty of Junonia hedonia, quite a few Crows, Evening Browns and Dingy Bush Browns but (still) no Eurema. There are increasing numbers of Eggfly, both Common and Blue-banded but (curiously) all male. There are one or two male Cairns Birdwings around, too, but no females. I wonder why? My best guess is that gender balance is somehow controlled by humidity, so that there are not too many caterpillars until there is ample food for them.

What else do we have? A few sap-sucking Shield Bugs, like the one above but smarter; the occasional Ladybird and Giant Grasshopper; just one dragonfly and one praying mantis in the last couple of weeks; and quite a few tiny moths, although the only moth big enough to notice is the Magpie Moth. And so it goes … I think we’ll need some good rain before we see more activity. Latest predictions are that we’ll get quite a lot from La Nina, though not as much as we had last year.