Archive for May, 2012
DRAGONFLIES and DAMSELFLIES – THE ODONATA
By Amy Prendergast
If you go for a stroll by a lake or wetland on a warm spring day or are fortunate to boast a pond in your own backyard, you are likely to have encountered these delicate insects skimming across the water surfaces, sunlight glinting off their delicate wings. Dragonflies and damselflies belong to two suborders – Epiprocta or Anisoptera (dragonflies)
Zygoptera (damselflies) – of the insect Order Odonata (Odonates). Odonates are easily recognizable by their 2 pairs of long, transparent, wings with lace-like veins, elongate abdomens, and bulging compound eyes that occupy most of the head.
Dragonflies and damselflies share similar biological features: both are carnivorous, inhabit areas around water bodies, and lay eggs that hatch into aquatic larvae. They can put on amazing aerial acrobatic displays, speedily manoeuvring and darting about in the air.
Males are very territorial and you’ll often see a male respond aggressively to any other males that dare invade his territory by chasing them away at high speeds.
If you see dragonflies flying in a paired formation, you’re actually observing part of the courtship between a mating male and female. Following a female Odonate’s consent to her suitor, she allows the male to clasp the back of her head (dragonflies) or thorax (damselflies) using a pair of copulatory structures (cerci) on his abdomen. Once attached, the male’s sperm produced in the 9th segment of his abdomen are transferred to the 3rd thoracic segment – where the male’s sperm sac is located – by curling the tip of his abdomen under itself. Once the sperm are transferred, the female raises her abdomen so the tip connects with the 2nd thoracic segment of the male and she receives his sperm, which can then fertilize her eggs.
Following mating and fertilization of her eggs, the female then lays the eggs in a nearby water source. After hatching the larvae and juvenile stages, known as nymphs, remain in the water. The nymphs have a very different appearance than the adults: they are fully aquatic and bear gills, lack wings, have much shorter abdomens, and a major difference between the adults and nymphs is how nymphs feature a distinct structure on the underside of their heads called a mask. Folded when not in use, the mask is rapidly fired outwards to capture prey with a pair of grasping hooks at the tip. Nymphs have voracious appetites, actively preying upon other aquatic invertebrates and even fish and amphibian larvae. Once the nymphs have completed their juvenile development, they emerge out from the water onto surrounding vegetation, moult their nymphal skin (known as the excuviae), and metamorphose into adults with fully-formed wings.
Whilst having similar biological characteristics, and also appear very similar, there are a few key structural features allowing you to differentiate between dragonflies vs. damselflies:
- Dragonflies have more robust, larger, broader bodies. The hind wings are broader than the forewings, and when perching, a dragonfly holds its wings out horizontally, perpendicular to the body. Dragonflies tend to dart, rapidly zipping about in flight. Their large eyes meet at the middle of the head.
- Damselflies have more delicate, slimmer, smaller bodies. Both pairs of wings are of similar size, and they flutter and hover in flight. When perching, the wings are laid-back vertically parallel along the length of the body. Their eyes are separated by a thin segment.
Originally found in 1996 near Inverloch at dinosaur cove. The find was part of a dig by Monash University and Museum of Victoria. An original jaw bone has provided some amazing clues to the now called Qantassaurus intrepidus. The bones are believed to be from 115 million years ago. See original article Volume 1 no 2.
The jaw is slightly stubby, likely to be around 2 meters high. It ran on two legs and fed on plants.
The replicas of this dinosaur are available at Museum Victoria and Australian Museum in Sydney. It was called Qantassaurus after the Australian airline Qantas which had shipped fossils all over the country for a prior exhibit.
Found this 2 years ago in the yard. A large web and a spider the size of a small hand! Told its harmless. Looking around the web (literally), its quite strong and would no doubt catch a large amount of bugs. The reference said it could hold a small bird.
The Golden Orb Spider is found across eastern Australia with other species elsewhere
. Common in gardens.
On a recent rescue we found this Brush – tailed possum (Trichosurus vulpecula), inside a building. Often possums especially brushies, just get into a pickle. We had to check this fellow since it had been reported in the building for a week. I just love my brushies, they have such a character and each one is ingrained with their own traits and personality.
While some possums can be difficult, this one was all heart. We found some minor abrasions and had a wildlife vet check it all over. The Ok was given and we released it with a possum box back at its original location.
Complete Guide to Finding the Birds of Australia
Richard Thomas, Sarah Thomas, David Andrew and Alan McBride
Price: $49.95 Published: March 2011
Publisher: CSIRO Publishing
456 pp., 5 1/2″ x 8 3/4″
maps, b/w & color photos
Edition: Second Edition
* Divided by geographical area according to ease of finding each species
* Covers all endemic and resident species plus migratory species expected most yearsFirst published in 1994, The Complete Guide to Finding the Birds of Australiawas the first ever book of its type – a complete guide to locating every resident bird species in Australia. This fully revised second edition expands on the best-selling appeal of the first, describing the best-known sites for all of Australia’s endemic birds, plus regular migrants such as seabirds and shorebirds. It covers all states and territories, and is the first guide to include all of Australia’s island and external territories.Profusely illustrated with color photographs of interesting, unique or unusual Australian birds, this book is a must-have for all birdwatchers.
How to use this guide
States and Territories
3. New South Wales
4. Australian Capital Territory
6. Northern Territory
7. Western Australia
8. South Australia
9. Australia’s islands and external territories
10. Pelagic birding
This book originally arrived in 1994. It was the beginning for the concept of where to see wildlife. The authors detail in this latest edition, the places to Australian resident birds. “Twitchers” bible if you like.
Geckos are small reptiles belonging to the lizard family Gekkonidae. These little lizards are characterized by a suite of some truly amazing features and traits, which include:
- Caudal autotomy: as a defence strategy, geckos are able to ‘drop’ their tails when seized by a predator, leaving the predator with just a tail, whilst their owners, whilst tail-less, are free to live another day. The tail eventually regenerates but interestingly it is usually a different colour and less patterned than the ‘original.’
- Oviparous: all geckos lay eggs (rather than giving birth to live young). They have very small clutch sizes, most only laying clutches of 2 eggs. Some species (or populations of a species) are actually parthenogenetic: all of the individuals are female and reproduce asexually via a mode of reproduction akin to cloning, producing genetically identical daughters.
- Small, round scales: their body surface is covered by many tiny, rounded scales. These scales are not particularly thick and so geckos are soft-bodied reptiles and lack the heavily-armoured body surface afforded by heavily keratinized scutes like those of crocodiles.
- Adhesive toe-pads: geckos have amazing climbing abilities and many of you will encounter them on vertical window panes or hanging unfazed upside-down on your ceiling. Their remarkable climbing ability owes to how a gecko’s toes bear large disc-like pads at the toe-tips. The amazing adhesive properties of the toes result from how these toe pads (also called subdigital pads or scansor pads) feature many transversely expanded rows of plate-like scales, known as scansors. Each scansor is covered with tens of thousands of microscopic projections (setae), each of which in turn bears one or more spatulate-shaped projections (spatulae). The microscopic spatuale on the tips of the setae create a very large surface area on the toes which exploit molecular attractive forces – known as Van der Waals forces – that enable them to grip to the smoothest of surfaces. This mechanism differs from that seen in tree frogs whose expanded toe pads adhesive properties result from capillary adhesion relying on a layer of liquid between the microscope cells of the toes and the substrate. Rather, in geckos this system is a dry adhesive system (doesn’t require water) with the bonding strength resulting from molecular attraction between closely associated surfaces due to changes in the distribution of electrons (the Van der Waals forces).
- Nocturnal lifestyle: almost all geckos are active during the night; during the day the escape the unwanted attention of predators and heat of the sun by hiding in crevices, burrows, under exfoliating bark, and in cracks in walls, trees or rocks. As an adaptation to their nocturnal lifestyle, geckos are characterized by very large eyes which have cat-like pupils.
- No eyelids: you’ll never see a gecko blink because they lack eye-lids! Instead the pupils are covered by clear discs that are periodically cleaned with the gecko’s tongue.
- Carnivorous: Upon emerging from their daytime retreats, geckos prey upon flying insects, but also eat other insects and spiders, and larger gecko species may consume smaller geckos and other lizards.
- Vocal: unlike many reptiles geckos have an extensive vocal repertoire, communicating frequently by emitting squeaks, buzzes, and chirps
Geckos have a cosmopolitan distribution, their range extending across the globe where suitable habitats exists. About 110 species occur in Australia. The charismatic little creature shown here, the Western Marbled Gecko (Christinus marmoratus) is endemic to southwest WA, its distribution being restricted to the cooler regions of southern parts of the state.