Microfauna (3) flies

When I started taking a real interest in invertebrates, flies were the group that surprised me most. Time after time, something I thought was a wasp or bee, even a dragonfly, turned out to be a fly. As the Queensland Museum says,

Flies belong to the Order Diptera. In Australia there are almost 7500 described species in 100 families. … Many sorts of insects are called flies but “true flies” are a distinct group of insects which have only one pair of wings, unlike the caddisflies, scorpion flies, mayflies and butterflies that have two pairs of wings. … True Flies are found everywhere, and include delicate craneflies, mosquitoes, and midges, as well as robust horseflieshouse flies and blowflies. …

If the stereotypical response to spiders is “Eeek!”, the response to flies is “Yuck!” Both responses are unfair, if only because of the enormous diversity of these families: many, probably most, of them are not at all scary and not at all disgusting in their habits. The QM again:

Biting, blood-feeding flies such as mosquitoes, midges, horseflies and blowflies are able to transmit diseases to humans and domestic animals. … But most flies are not pests, most are important decomposers of plant and animal matter.

This page doesn’t include any of the Diptera that we don’t usually think of as flies, e.g. mosquitoes and midges. None of them are as big as a house fly, which is 5 – 8 mm long, and most of them, like most of my tiny spiders and miscellaneous other tiny insects posted recently, are 2 – 5mm.  I don’t know much about some of the species pictured here, because they are so small they have escaped even my notice until recently, but I will give what information I can.

fat red fly with barred wings
Signal fly, Platystomatidae, Rivellia sp., about 4mm long.
slim brown fly with long legs
About 6-7mm long but very slim, probably a crane fly, Tipulidae. Resting on a Dianella lily.

Crane flies often don’t feed at all as adults, living only to breed. When they do feed, they feed on nectar. Bigger relations of this little one are very common, and here is a picture of one sipping from mango blossom.

Squat black fly with red eyes
Only about 2mm long but built like the proverbial Mack truck. Why? I don’t know. What is it? Ditto.
Colourful fly
2-3 mm long and strikingly coloured, and that’s about all I know.
metallic green fly with black-banded wings and abdomen
A Long-legged fly, Dolichopodidae, probably Austrosciapus connexus, about 4mm long.

The Long-legged flies are tiny counterparts to dragonflies in that they are swift, agile aerial predators. They are common in my garden year round but are very difficult to photograph because they are so fast – they usually jump at the beginning of the flash and show up as a blur on the edge of the picture. Dragonflies are not true flies, of course (they have four wings). One small indication of the diversity of our flies is that there are almost as many Australian species of this one family (about 320) as there are of all Australian dragonflies.

Most Dolichopodidae that I see are metallic green or gold, but some are less showy:

Long-legged grey fly
Dolichopodidae again, a little larger than the one above.

More about flies: CSIRO entomologyWikipedia/Fly.

Microfauna (2) spiders

Here is my second gallery of little creatures, not insects this time (they are here) but arachnids. No need to worry, though – they are tiny, so small they are completely harmless to us as well as almost invisible.

small grey spider
A very young St Andrew’s Cross spider, Argiope keyserlingi. Her web is faintly visible behind her.

Spiders are more like us than like insects in that they don’t change their form as they grow: they are already recognisably spiders when they hatch from their eggs, and they simply get bigger. However, they have rigid exoskeletons like insects, so they can only get bigger by moulting, and some species change colour as they mature.

The familiar St Andrew’s Cross spider changes colour significantly. The 2mm individual above is the greyish-brown of newly-hatched spiderlings but (if she survives) will turn orange-brown with similar coloured stripes, then the stripes will become more distinct, and finally her background colour will darken. Here is an adult.

Tiny yellow spider on leaf
This tiny spider (head and body about 2mm) built its tangled web across a cupped basil leaf. Theridiidae, Anelosimus group.
small translucent brown spider
Stucco spider or Wall spider, Oecubius species, on a shelf in my workshop. Head and body 2mm.

Some species of spiders just never grow very big, and these two are good examples. The second lives amongst us (if you’ve noticed a wisp of silk in a tiny groove or hollow on your walls or a cupboard shelf, there may well of have been one of these behind it) and has therefore acquired a common name. The first, however, is one of many species living anonymously in our gardens. Saying it is in the ‘Anelosimus group’, as my friendly spider expert did, is about as precise as saying ‘some kind of dog’. It is often the best we can do, however, since so many tiny critters remain scientifically unknown and un-named.

Spider and prey
A small spider (3mm), perhaps Nephilengys sp., with prey which seems to be a plant-hopper.
Spider and prey
Another view – click for larger versions

 

 

 

 

 

 

 

 

 

Deciding whether a particular spider is an adult or not can be problematic unless we recognise the species and know how big they usually grow. In this case, I don’t really know but I’m pretty sure that this is nearly as big as it gets because I would have noticed them in my garden long ago if they grew much bigger. After all, I know the Lynx (pretty photo), Flower Spiders (lots of photos) and Jumping Spiders (lots of photos) well enough, and they are all usually under 8mm.

small square brown spider
Austracantha male, about 2mm square.

Male spiders of most species are smaller than the females, often a lot smaller. This little bloke is the male of the common spiky black and white Jewel Spider or Christmas Spider.  He is about 2mm square, while she is about 8mm. Other examples of this size difference (aka sexual dimorphism): Flower spider and Golden Orb-weaver.

Orb-weaver and tiny spider in web
Just friends: an orb-weaver with a tiny spider of another species, probably a Dewdrop Spider. The larger one is about 8 mm long, so the smaller is only about 1 mm.

If you see a tiny spider in the web of a much larger one, it isn’t always a male of the same species. Dewdrop spiders, for instance, are tolerated in webs of larger orb-weavers (Neoscona sp., about 8mm, is in the background here but St Andrew’s Cross and even the enormous Golden Orb-weaver are known hosts), living on scraps and maybe accidentally-caught tiny prey.

Lynne Kelly has said, in Spiders – Learning to Love Them, that wherever we are in the world there is likely to be a spider within a metre of us. I’m sure she’s right, but would add that the reason we are not constantly aware of them is that most of them are so small.