I am an ant! Really!

Ant-mimicking Hemipteran nymph uid 5268I lie.

I am not actually an ant at all, but looking like one may save me from critters willing to eat harmless vegetarian bugs like me but unwilling to attack nasty-tasting, big-jawed ants.

Starting again, a bit more seriously: these photos show a couple of insects I found together in my garden recently. The first is about 6mm long, the second about 8mm. My first and only thought was that they were ants, although the transparent rim around their bodies looked strange for an ant (and just as strange for anything else) and so did the bracket-shaped shoulder-piece of the larger one.

Ant-mimicking Hemipteran nymph uid 5253I uploaded both photos to my Flickr photostream and the good people from the Field Guide to Australian Insects and Encyclopedia of Life Images soon put me on the right track: “I’m guessing that these are close to the Broad-headed Bugs (Alydidae). Both seem to be immature stages and the wings have yet to develop completely. The adult would have wings covering the abdomen,” and, “not an ant but an Hemipteran nymph … it vaguely resembles other ant-mimic bugs in the family Nabidae I know from Europe,” and, “Definitely an ant-mimicing heteropteran nymph. We (Aussies) have numerous species spread among several families that have ant mimics as nymphs,” and, “Semi-transparent seams give the impression of several constrictions, where there are none!” (Clicking on the images on this page with take you to Flickr, where you can see the whole discussion as well as full-size photos.)

In this light, the puzzling features weren’t so odd: I know a native cockroach  and a beetle which have transparent edges to their coloured carapaces, and the ‘shoulder-piece’ is simply a pair of wing-buds.

Once the right track, I succeeded with an image search. The best match I found was on Brisbane Insects’ invaluable site, Rhyparochromidae – Seed Bugs, which told me that Rhyparochromidae is a family closely related to Lygaeidae (Seed Bugs, Milkweed Bugs and Chinch Bugs). They are small dull brown or blackish bugs which eat seeds; many of them are flightless.  When (if) my bugs become adults, they should look something like this or this (not my photos), with wing patterns mimicking the ant-like body segmentation.

These bugs are far better ant-mimics than the jumping spiders I found a while ago. Some of their relations are pretty good, too – visit Brisbane Insects’ ant-mimicry page to see them.

Excessive antennae

Katydid nymph
Look at my antennae, everyone!

Katydids are closely related to grasshoppers and crickets (they are all classified as Orthoptera), and the easiest way to tell katydids, at any age, from grasshoppers is the length of their antennae.

This little one (8-10mm long) seems to have overdone it somewhat but is perfectly normal – see, for instance, a differently coloured one I photographed in April. When it grows up it will look something like this or this, but it is often impossible to know the exact identity of a juvenile insect.

Katydid nymph front view
Face to face with the same nymph, with the antennae blurred to invisibility by depth-of-field limitations of the camera.

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.

Growing Giant Grasshopper

Giant grasshopper nymph (Valanga irregularis)
Immature Giant Grasshopper, Valanga irregularis

As the Wet settles in, the plants are growing like crazy and the herbivores take full advantage. When this young one has moulted another time or two, sex will become as important as food (see this photo, for instance) but the one imperative of a Giant Grasshopper nymph is very simple: Munch!

Moulting

Insects and spiders can’t grow steadily like we do because their skeletons are on the outside and serve simultaneously as skin, skeleton and armour. It doesn’t grow or stretch once it has hardened so the animal has to grow a new skin underneath the old one, crack the old one open and crawl out, and wait nervously until the new one toughens. I have seen different parts of the process in different insects recently so I thought I would put a group together.

Dragonflies: Juvenile dragonflies are so different from the adult it is hard to believe they are even related. They are water-dwelling predators which fishermen know as ‘mud-eyes’ and use as bait. After several moults in this form they climb up out of the water and split open to emerge as the winged adult dragonflies we know and love. I have yet to see it happen but here is a lovely photo from SE Qld.

Cicadas: Cicadas also undergo a radical change, since the nymphs live underground, emerging as stumpy-looking bugs with strong burrowing front legs and splitting open to emerge as a winged adult. I haven’t seen one emerging but here is a cast-off skin (known as an ‘exuvia‘), and here and here are some adults

Cockroaches: We have a resident population in our compost bin and I caught this photo recently of a just-moulted cocky resting next to its old skin. Like many (perhaps most) insects, fresh-moulted cockroaches are nearly colourless as well as soft; they darken as they harden.

Mantises: I found this cast-off skin eighteen months ago but I didn’t see one in the process of emerging until yesterday. It is one of the family I have been watching recently and described here. In terms of that post, this is a nymph with wing-buds emerging from one without. One photo of it is here and another is below.

In all cases, the amount of change from one stage (‘instar’) to the next is hard to believe. Even when they don’t change from swimmers or diggers to fliers, the difference in size makes you wonder how on earth that big bug fitted inside that little skin.

In human terms  the changes would be (roughly) like changing from a one-year-old to a three-year-old overnight, then to a six-year-old, to an eleven-year-old and finally to an eighteen-year-old. What a difference that would make to our lives!

Mantis nymph emerging from skin
Neomantis nymph emerging from a skin it has well and truly outgrown

Another kind of mantis

A month ago I wrote about finding a group of tiny just-emerged mantis nymphs. (‘Nymphs’ covers all stages of development except adults, from just-hatched to nearly fully developed.) In a footnote to that post I mentioned a larger nymph I discovered a little later. I have been observing and photographing that one and its relations (at least two more hatchings, all on a particular patch of weeds) since then and now have a reasonably complete record of their development.

First, the hatchlings (click on any photo for a larger image). They are quite different from the ones in my previous post. Most obviously, they are paler and have pairs of brown spots all the way along head and body. Also, their head is much broader than their thorax, and their typical posture is different: straddle-legged and straight-backed.

Neomantis nymph
Spotty nymph

Mantises moult to move on to the next stage – the next ‘instar’ – of their development. The next stage I recognise is still completely wingless but the brown spots have faded. One or two instars later, wing buds appear; they have a faint mottling of darker green, as do the front legs. The nymphs are still straddle-legged but a new characteristic posture appears: they flatten themselves against the leaf they are on. They spend more time underneath their leaf than on top of it, at least by day.

Neomantis nymph older
Older nymph
Neomantis nymph
Nymph with wing buds 1
Neomantis nymph
Nymph with wing buds 2

 



Finally, the adult, about 20 mm long: the broad wings are translucent (note the leaf veins visible through them) and marked in a pattern of dark and light veining which resembles the pattern of the leaf itself. Around the ‘shoulder’ of each upper wing is a short row of yellowish spots, with minute black dots between them.

Neomantis adult
Adult 1
Neomantis adult
Adult 2



So what is it? Certainly a mantis (Mantodea, Mantidae) but not the common  green Garden Mantid (Orthodera ministralis). It looks much more like the mantid shown here as Neomantis australis, but that one is still different in several ways: it has narrower wings, is more nearly transparent and yellower overall, and has dark eyes (which may be due to the fact that it is a photo of a dead insect). CSIRO’s (poor) photo of Neomantis australis shows an insect more like mine but with a transverse pale stripe across its wings, more like the one I saw on Hervey’s Range.

I suspect there are at least two species or sub-species amongst all these but for now I will just call my little family Neomantis australis with one or two question marks.

Just out: praying mantises

We’re still waiting for rain but the warmth and humidity seem to be encouraging some insects to emerge anyway. I wrote about cicadas a few days ago, and on Sunday I spotted first one, then a dozen, tiny praying mantises on the railing of our back stairs. Here’s one:

very young praying mantis
Giving thanks for a safe emergence?

The picture is much larger than the mantis, which was only 8 – 10 mm long.

Figuring that there had to be a good reason for a group of infants to be together like that, I looked around and found their egg-case (ootheca) glued beneath the railing:

The egg-case or ootheca, with the popped cell-lids dangling from it
The ootheca, with the popped cell-lids dangling from it.

P.S. Here is an older nymph – more than twice the size – a fortnight later. I’m pretty sure it’s not one of these babies grown up, though, because it was too far away.

P.P.S. (Dec 28): The nymph I linked to now seems certain (as I have observed its development) to have been a different species of mantis from the one pictured above.