I spent most of today with a fly. That may seem like a huge waste of time, but this was no ordinary fly – it was a wallaby fly. The closest I usually get to one of these flies is when I see a wallaby in the garden furiously flicking its ears trying to dislodge one. The individual here took a liking to me in the garden, and hitched a ride inside.
Flies of the family Hippoboscidae are all blood-sucking ectoparasites,
i.e. parasites that live on the outside of their hosts. These flies usually
cling to the hair of mammals or feathers of birds depending on the fly species
involved. They have characteristically flattened bodies, powerful legs, and fishhook-like
claws (clearly visible in the image below). You can see now why they are known
generally as ‘louse flies’. There are more than 200 species found throughout
the world (30 species here), and about 75% of them are ectoparasites of birds.
Hippoboscid flies are quite particular about their hosts, for example flies which feed on mammals are not found on birds or vice versa. Back in the 1930’s research was conducted to determine if pigeon louse flies (Pseudolynchia canariensis) could bite humans and survive on human blood. The conclusion? They will bite humans when given no other choice of warm-blooded host. In other words, only when they are forced to. In case you were wondering – I wasn’t bitten.
Farmers in cooler regions of Australia may remember the introduced hippoboscid species Melophagus ovinus known as the ‘sheep ked’ or ‘sheep-tick’. In the past heavy infestations of this pest could cause anaemia in sheep, but modern farming practices have made occurrences of this pest quite rare. If you want to know more about this pest go here.
While reading about hippoboscid flies I learned a new phrase – ‘adenotrophic viviparity’. I was familiar with ‘ovoviviparity’, where eggs are held within females until they hatch internally, and the females give birth to live young. The picture above shows a green peach aphid doing just that. Adenotrophic viviparity is where eggs hatch inside the female, and the larvae are fed internally until they are mature enough to pupate. The larvae pupate immediately after being deposited by the female. The vulnerable larvae are therefore only momentarily exposed to predators.
I photographed the wallaby fly on the back of my hand in an
attempt to show that it was a bloodsucker. It was also a skittish critter! Towards
the end of the shoot it flew off my hand and landed on my black T-shirt – camouflaging
it beautifully. It wasn’t until it crawled onto my face that I knew where it
was. “Perhaps I’ve got enough photos now”, I thought. I hastily retrieved the
fly and released it outside. Look out wallabies!
Footnote: Many of you will have noticed that my post title (Don’t Fear) The Hippoboscidae references the 1976 Blue Oyster Cult classic (Don’t Fear) The Reaper. This song has had several lives including the original (link), the merciless Will Ferrell et alparody (link) – where the line ‘more cowbell’ originates – and the fun version with cowbell (link) by Leo Moracchioli.
You would think that a spider as robust (and venomous) as a huntsman spider (Sparassidae) would be pretty safe from predatory and parasitic insects. But not so. This article is the first in a series on the insects which make a meal of large spiders.
A few years ago I witnessed a titanic struggle taking place on a window at the front of our house. A large spider hunting wasp (or ‘spider wasp’) was pulling a huntsman spider backwards up the window glass.
This spider is a female of the species Cryptocheilusbicolor of the order Pompilidae. These gorgeous black and orange wasps find a large spider and sting it to paralyse it.The female spider wasp doesn’t feed on the spider herself – the spider is food for her offspring.
Earlier that day I had seen our wasp digging a nest hole in the sand bank at the rear of our house. Many species of spider hunting wasps place their prey in a nest in the ground (one spider per cell) and lay a single egg on it. The hatching wasp grub feeds on the live but immobilised spider.
I saw her trying to fly with the spider but she could barely lift it off the ground – her wings were damaged as you can see from the image above. Dragging the spider was her best option and she was attempting a shortcut up over the house rather than going all the way around!
The glass was slippery and the spider was heavy and down down down she would slip – sometimes all the way to the ground. Each time she fell down she started the climb again. I have no idea why she insisted on going up glass rather than up the house bricks where she would have had more grip.
Eventually after about half an hour of this frustrating struggle she gave up and began hauling the spider around the house – a distance of about 50 meters. She accomplished the task of dragging the spider to her nest in just a few minutes. After about an hour she emerged from the nest and flew away. I assume she had laid her egg and had no more interest in the nest.
When spider wasps move around on the ground they move in a jerky ‘stop start’ manner and constantly flick their antennae and wings. The video below shows typical spider wasp behaviour (featuring a different individual to the one described above).
There are about 230 species of spider hunting wasps (Pompilidae) found in Australia. This is only one of the groups of insects which attack spiders – there are many more. The image below shows some insects from one such group. What are they? You’ll have to wait for the next ‘one minute bugs’!