Green-ant and mealybug

Green-ant tending a lone mealybug on a fern frond
Green-ant tending a lone mealybug on a fern frond

Green ants (Oecophylla smaragdina) are a big feature of life in North Queensland. A lot of people dislike them for the very good reason that they sting but I don’t mind that too much because they are, after all, only defending themselves and they are fascinating to observe. I particularly admire the way they co-operate to make their nests.

They are among the many species of ant which have an amicable relationship with mealybugs. I don’t like mealybugs (Hemiptera, Pseudococcidae) as much as I like the ants, to be honest. Yes, I know mealybugs are only doing their best to survive, just like every other living creature, but they don’t do anything interesting and they do damage the plants they live on.

Yates Problem-solver gives the gardener’s perspective on them:

Mealybugs are small insects covered with a white mealy coating; some have white hairs attached to their bodies. The bugs feed by sucking on the plant juices. Mealybugs excrete a sticky substance called honey dew which ants like to feed on. The honeydew also provides a perfect medium for sooty mould growth. Mild temperatures and high humidity are perfect conditions for mealybugs to breed as eggs hatch every 2-3 weeks. Prolonged hot weather reduces numbers. Heavy infestations can occur on citrus trees, daphne, and other ornamental plants. Orchids and ferns, especially in shadehouses, can also become infested.

There is more on mealybugs’ life cycle and control strategies at About.com and The Spruce.

Heading for higher ground

I started my monthly survey a couple of days ago by mentioning that it was raining …
According to the BoM, Townsville Airport had 36 mm from 9.00 a.m. Thurs to 9.00 a.m. Friday and 91 mm from then to Saturday morning. It was patchy, though, with bands of rain coming through, and we measured 125 mm here from Friday morning to Saturday morning. That turned the bottom of our yard (near the bananas, which love water) into a floodway. Genuine Wet-season rain!

It has prompted a couple of colonies of small ants to head for higher ground – more than a couple, I’m sure, but those I saw were both on my window-sill. One trail was outside the window and the other emerged from under the sill inside the room, and went up and over it to points unknown. The ants in both trails were so small that I couldn’t see they were different species until I saw my photos on screen.

Species 1

Ants carrying eggs
Ants on the outer window sill, one (foreground) carrying a larva and one with an egg

Not all of them were carrying eggs or larvae. Some were returning for a second load, while others were apparently just moving with the crowd.

Ants on window-sill
Fellow-travellers. The white one may be newly emerged

Species 2

Ants of the other species, coming from inside the wall, are more uniformly brown and I think they were a little smaller, though it’s hard to pick the difference between 2.5mm and 2mm when they are all moving as fast as they can.

small brown ants with eggs
Three ants going upwards, one with eggs, and one returning.

 

two small brown ants
The slightly larger ant looking back down the trail may be a soldier guarding the line of workers.

Seeing ants heading for high ground is a classic warning of more rain to come, of course. The BoM agrees: the Low in the Gulf is expected to become a weak cyclone in a day or so and funnel a lot more rain our way. But the Dove Orchids didn’t flower early last week to warn us, as they are supposed to … I’m losing faith in their reliability, I’m afraid. Or maybe they just can’t react to changes in humidity when the average is 99%.

Nocturnal visitors

Black and green dragonfly, family Telephlebiidae
Dragonfly attracted to house lights

We have a constant stream of nocturnal visitors.

Most of them have six legs and arrive by air.

We don’t appreciate those which would like to suck our blood (mosquitoes are a pain), but the others are welcome enough. The dragonfly above was larger and more handsome than most and didn’t mind posing for a series of photographs, although I do think he has been unduly influenced by the trend for picking grimy industrial backdrops for fashion shoots. I mean, really, there are more attractive settings than the scrap timber stored under the house.

Fawn moth on desktop
Small moth

This tiny moth, about 7 mm long, is a more typical guest, flying into the house and landing on my desk. A look at my Flickr photos reveals the bizarre moth-fly (a fly that looks like a moth, not vice-versa) on the same background a couple of months ago and this beautiful olive-green moth on the wall nearby. If I left the windows wide open and the lights on, I could have hundreds like this instead of only tens.

Just now, flying ants are common. As I said about the Green-ant queen, warmth and moisture induce the emergence of swarms of winged ants on their way (they hope) to breed and set up new colonies. The one below failed spectacularly, coming to rest on … my mouse.

Black ant, winged
Flying ant on alien artifact

Queen green-ants

North Queenslanders know green-ants very well. Their nests of woven leaves are common in our trees, and we learn to be cautious about pushing through shrubbery because the workers drop on intruders and bite quite painfully. But there is one stage of the life cycle we rarely see: the winged queen.

Large winged green ant
Winged queen green-ant

Unmated queens-to-be fly from existing colonies in the wet season and, if they are lucky, mate with winged males released at the same time and then establish their own new colonies.

We visited Magnetic Island yesterday and saw dozens of the winged queens. They looked like wasps but were clumsy fliers, often crash-landing into plants or people, and in spite of their powerful jaws they were not at all aggressive.

Green-ant queen
Another, sitting on my finger

The queen, like all flying ants, soon loses her wings. She will find a likely spot for a nest, and start laying eggs, and her children/workers will build the nest around her.

More pics: Worker and Nest construction  on Flickr.

All you ever wanted to know about Green-ants: A masterpiece of evolution – Oecophylla weaver ants by Ross H. CROZIER†, Philip S. NEWEY, Ellen A. SCHLÜNS & Simon K.A. ROBSON, Myrmecological News, 13, 57-71, Vienna, April 2010 (pdf)

Mimicry again – ant-spider

Small red and black insect
Ant? No, spider – Jumping Spider, in fact

A few days ago I showed a fly pretending to be a wasp (at bottom of previous post). On almost the same day I saw a little insect 5-6 mm long scurrying around on the broad strap-like leaf of a lily. It looked like an ant, but somehow not quite right. The camera let me stop it and magnify it, and see that it was in fact a spider.

Merely counting  the legs is enough to make that judgement, but we can go further. Looking at the eye pattern (you may need to click on the image to see the detail) puts it into the large family of Jumping Spiders, Salticidae. As roaming hunters, salticids depend totally on good eyesight and their upper central eyes are very large and face forward.

I was quite puzzled the first time I saw one (the one below), almost exactly a year ago: the body is very ant-like and the front end is … bizarre. We expect spiders to have two distinct sections, head (technically ‘cephalothorax’) and body (abdomen) but this one seems to be in three sections, with two fat rods sticking out in front of the head – as big as the head, too. They are actually its jaws, enormously enlarged to give it more of a three-part ant profile.

black ant-mimicking spider
Another ant-mimicking Jumping Spider

I haven’t been able to completely identify either of these two. I am fairly confident they are Myrmarachne species but haven’t found any just like them on the web. I don’t feel too guilty about that because there are ‘nearly 80 described species and more to come’ according to the experts. There’s a user-friendly introduction to them here, on the excellent Brisbane Insects site, and another here, on Arachne.org.