Saturday, December 18, 2010

Assassins on the prowl

We have spent the last three months filming a TV series on predatory bugs, and some of the predators we have been working with are the assassin bugs. They are incredible insects that hunt by stealth, then stab their victims with their long proboscis and paralyse it within seconds.

Watching them hunt is amazing. Once they detect prey they will approach it with such caution that they hardly seem to be moving at all. All the while they keep tabs on their intended prey with extremely long mobile antennae. Sometimes the strike is rapid, but other times they try to sneak in a little lethal injection without the victim noticing. Once the victim notices the little sting it is all but over. The assassin bug then feeds on the victim via its proboscis, and discards the empty husk when finished.

 
A delicate orange assassin bug from our garden. This species is a ready flyer.

The same species feeding upon a grasshopper.
One of the giants, a Bee Killer Assassin Bug Pristhesancus plagipennis found about 10 minutes west of Kuranda
A close-up of the proboscis of Pristhesancus plagipennis. This species can capture very large insects.

Wednesday, December 15, 2010

Mini ambush hunters

Both these tiny spiders are hunting in our front yard. The yellow crab spider (Thomisus spectabilis) is a flower-top hunter. This species waits in ambush for flower-loving insects. They can catch prey up to the size of a honeybee, many times their own size.


Crab spider, Thomisus spectabilis. Crab spiders are so called because of their ability to move sideways.
The Triangular spider (Arkys sp.) is another ambush hunter which sits and waits upon leaves for passing prey. Although these two spiders are unrelated, they both share similar adaptations to assist them to snatch and hold their prey.
Triangular spider, Arkys lancearius

Monday, December 13, 2010

Nocturnal visitor

We were returning from a recent night walk, and had practically reached our front gate when we had a chance encounter with another invertebrate lover. This one, a Striped Possum (Dactylopsila trivirgata), prefers to eat the invertebrates it finds. Striped Possums have an elongated 4th finger and use it to hook out wood eating grubs from within the trees. They also use their teeth to tear open the timber to expose the insects. The diet of this species is not just confined to insects, they also feed upon fruits, leaves, and will dine out on the honey of native bees if they are lucky enough to find some.


The Striped Possum just opposite out driveway. It dissapeared very quickly after this photograph. 


Sunday, December 12, 2010

Bright orange amongst the green

It seems that being bright orange and yellow is the recipe for success in the rainforest for several species of Australian huntsman spiders. Compared with the grey-brown camouflage colouration of most of the southern species in the Sparassidae family, many of the rainforest huntsmen are simply stunning.

This week I have encountered two brightly coloured species in the genus Beregama. Beregama cordata, the Fireback Huntsman, and Beregama aurea, the Golden Huntsman. The latter is a huge spider and is considered the second largest species of huntsman in the world behind Heteropoda maxima from Laos.

Previously in this region we have encountered the orange/yellow Sunburst Huntsman and the Tiger Huntsman, both of which are undergoing classification.

Why bright orange? As juveniles these spiders are quite dull and cryptic, but they progressively adopt the brighter colouration as they grow. As adults, they often stand out like beacons within their habitats. Whether the colours are just for warning away predators or for some other purpose I cannot say. It does not seem likely that it is for courtship puposes as the vision of this group is quite limited, and courtship seems based upon pheromone detection and tactile interaction.

 

A huge male Beregama aurea, 4km west of Kuranda
 
A female Beregama cordata at Cape Tribulation
A Sunburst Huntsman from Cape Tribulation in 2006
The female Tiger Huntsman we found near Cairns in 2006. (This was the first record of this species and is currently at the South Australian Museum awaiting description)

Wednesday, December 8, 2010

Spider identified and mantispid emerges

We have identified  the crab spider as Poecilothomisus speciosus (thanks Colin). It is the sole member of the genus in Australia, and is only found in north eastern Queensland. We are not sure why the Australian spider has been placed in a genus by itself, whilst the related overseas species are all members of Platythomisus - had me confused.

Today the eggs hatched but only a handful of tiny spiderlings emerged from the egg sac. The reason for this was because an invader had also been occupying the egg sac - a mantispid.  Mantispids are mantis-like Neuropterans and some species select spider eggs as food while they are in larval form. Mantispids use two strategies to access spider eggs; some larvae find an egg sac and burrow in through the silk, while other species hitch-hike upon the female spider and enter the egg sac as it is being constructed. We are not sure which strategy this particular species used, but it was successful.

The mantispid shortly after emerging from the egg sac.

Mystery spider

For the second time in recent years I have swung my torch around to reveal a brightly coloured spider sitting in a tree and knew that I was looking at something very unusual.

In 2006 it was the Tiger Huntsman which turned out to be the first recorded specimen of an undescribed species in the genus Typostola - it is still awaiting description. The fact that you can still find species that are new to science is one of the very exciting aspects of the wet tropics.

This time however, the spider may not be one that is undescribed, but one that is not well documented in Australia. Its movement and body form are clearly that of a crab spider; family Thomisidae. After some sleuth work I have managed to tentatively identify it as Platythomisus sp.. Around 20 species are recorded from Africa, through southern Asia, but apparently not in Australia.

The obvious question beckons: Is this an Australian species or is it an introduced specimen? The plot thickens further as I found this specimen peeking out of a curled leaf whilst incubating eggs.

I will endeavour to contact an arachnologist who has experience with Australian Thomisids to answer this one. Stay tuned!

The specimen is quite large compared with the majority of Australian Thomisids. Body length 14mm.
The markings on this specimen are quite stunning and are very similar to Platythomisus spp. found throughout Asia. It does have distinct differences though.
For a small spider it is quite aggressive and actually tried to bite my finger whilst I was taking these photographs.

One of the first things that struck me was the superficial resemblance to the spitting spiders Scytodes. Interestingly, one species of Platythomisus has been named P.scytodimorphus

Wednesday, December 1, 2010

Daylight robbery

This stunning fly is one of several species of Robber flies (Family Asilidae) that are active at the moment around our home. Robber flies are active hunters that catch prey in flight, or pluck it from foliage. They have huge eyes, excellent vision and a capacity to turn their heads rapidly to keep track of prey or threats. They feed through a large proboscis which is driven into their prey to extract its body fluids. Some species are nocturnal and we have observed them feeding on large cockroaches, but the species below is active by day. Robber flies will often fly short distances and return to the same area to wait and watch for potential prey, making them reasonably easy to observe and photograph.

This Robber fly is feeding upon a blowfly