Simply irresistible

The Grampians region of Victoria is one of Australia’s richest and most diverse flora areas. One third of Victoria’s flora is represented here so it is no surprise that the region was once dubbed “the Garden of Victoria” by the great botanist Ferdinand von Mueller.

Spring is an excellent time to see wildflowers throughout the region, especially terrestrial orchids such as the Mantis Orchid (Caladenia tentaculata) pictured below. It is one of the green-comb Spider Orchids and is common throughout the Grampians region. The colourful and flamboyant flowers of this orchid may be pleasing to the human eye but they are simply irresistible to certain male insects.

Caladenia tentaculata

The Mantis Orchid is one of many sexually deceptive orchids. Orchids such as these don’t have nectar to reward pollinating insects so they must attract insects some other way.  The orchids lure male insects to their flowers with scents that mimic female insect sex pheromones. The labellum of the flower where the male insect lands is hinged and swings the insect against the sexual organs of the flower. During its struggles to mate with the flower the insect will either pick up pollen, or deposit pollen that it has acquired from another flower.

The insect pollinator of the Mantis Orchid is a thynnine wasp of the family Tiphiidae. These wasps are the most important insects which pollinate Australian terrestrial orchids by pseudocopulation. The wasps are also remarkable because males are winged and females are wingless. A female wasp finds a mate by advertising her presence with pheromones, the male picks her up and mating occurs in flight. It is quite common to see mating pairs flying around our property. A mating pair of thynnine wasps is pictured below.

Thynnine wasps

All this flying around while mating means the wasps stay in a coupled position for a prolonged period of time. To facilitate this, both sexes have evolved unusually shaped genitalia that include spines, grooves and other structures, so that they don’t accidentally disengage. But why don’t the females have wings? Some female flower wasps are parasites of beetle larvae and mole crickets located underground. Winglessness allows females to dig underground and hunt for prey without risking damage to delicate wings. This probably sounds exotic and unusual, but wasps of the family Tiphiidae are common in Australia, in fact we have about 700 native species.

Thynnine wasps are not the only insects lured into pseudocopulation with native orchids. I think I have space for one more story which should be titled “How not to photograph a pseudocopulating insect“. One November some neighbours showed me Large Duck Orchids (Caleana major) flowering on their property. As you can see below they are spectacular flowers that resemble flying ducks, so I grabbed my camera for some shots.

Caleana major

Within minutes of me starting to shoot the orchids an insect arrived and landed on one of the flowers. “Holy cow”, I thought. “It’s the pollinator!” Heart racing I tried to capture the insect but in my excitement I tripped over my tripod and almost flattened the orchid! By the time I got myself organised the insect, a type of sawfly, was trapped inside the orchid and was barely visible. I did get a couple of shots of the insect emerging but they are pretty terrible (see below).

Duck Orchid pollinator

How did the orchid trap the insect? The ‘head’ of the duck is the lid of a trap which swings down by the ‘neck’ trapping the insect inside the ‘body’. In it’s struggles to escape the insect is covered with pollen and will transfer that to the next flowering Large Duck Orchid it is attracted to. Hopefully one day I can have another crack at these shots and try not to be overwhelmed by the occasion!

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Insect Architects

After a few months off for house painting one minute bugs is back!

I was prompted to write this post after completing an article for Hort Journal Australia on a similar topic. My argument in the Hort Journal piece was that insects are not mathematical or engineering geniuses, and that their behaviour is dictated by the instincts they have evolved with. All very scientific and anti-anthropomorphic. The post here is a bit different. Let’s marvel at the exquisite perfection of some of the structures that insects build.

Our first architects are moths of the family Psychidae – the case moths. These are harmless creatures found in most gardens throughout Australia. Cases are spun by caterpillars from silk to which twigs, sand, moss, lichen, leaves or bark are attached. The cases can open and close at each end, the front end for feeding and the rear end for ejecting droppings. I believe the species illustrated below is Lepidoscia arctiella – look at how precise those little bits of twig are!

Psychidae

Continue reading Insect Architects

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Cuckoos & cleptos

Most of us are familiar with the activities of avian cuckoos where a bird lays its eggs in the nest of a host bird of a different species, after kicking out the eggs that were laid by the host. We have a dozen or so species of cuckoos in Australia and some of them utilise the nests of birds half their size. The worst mismatch I have seen was a pair of exhausted Superb Blue Wrens (Malurus cyaneus) trying to feed a massive fledgling Fan-tailed cuckoo (Cuculua pyrrhophanus). The young cuckoo was never happy with the amount of food brought to it and constantly pecked its foster parents.

Did you know there are insect cuckoos too? Granted there’s not a lot of the bullying going on like in the bird example described above, but there is certainly similar amounts of clandestine behaviour. There are about 75 species in the wasp family Chrysididae in Australia, with common species being referred to as “cuckoo wasps”. They vary in length from about 6 mm to 22 mm in length and they are strikingly beautiful insects because of their metallic colours.

Chrysididae Continue reading Cuckoos & cleptos

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I love parasitoids

To most people the word “parasite” conjures up all sorts of images from tapeworms to brain-eating amoebas to scenes from the film Alien. So a “parasitic wasp” must be something really freaky and horrible then? To us – no; but to an aphid or a caterpillar or some other target insect – yes.

Technically a parasitic wasp isn’t a parasite at all. True parasites like tapeworms don’t normally kill their hosts, because that would mean their own death. So insects such as parasitic wasps and flies which parasitise and kill other insects are known as parasitoids.

parasitoid Continue reading I love parasitoids

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Revenge of the Mummy

Have you noticed swollen bronze-coloured aphids on your plants? These are aphid ‘mummies’ caused by the parasitic wasp Aphidius of the wasp family Braconidae. There are several species of Aphidius which have been released in Australia. A species that has established well and is common in urban gardens is Aphidius rosae, a successful parasite of the rose aphid Macrosiphum rosae.

Aphidius wasps are shiny black, slender insects about 3 mm in length with long antennae. The diminutive size of these wasps makes it hard to see them in gardens, but you will see the results of their life cycle within aphids. Adult female wasps lay their eggs singly inside adult aphids and aphid nymphs. To accomplish this a female wasp must bend her abdomen under her legs and inject an egg into the aphid with her ovipositor (‘stinger’). If you were watching and you blinked, you would miss it, as this operation takes less than a second. Obviously I don’t have many images like this one.

Aphidius Continue reading Revenge of the Mummy

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