The Silver Orb Spider (Leucauge dromedaria)

Leucauge dromedaria [SILVER ORB WEB]  Gordon's Bush, Whanganui, New Zealand 11-01-2018 (18).jpgClick to zoom in

Much like our previous spider post, the spider under the spotlight today (Leucauge dromedaria) is an Australian import that we found on one of our bush walks here in New Zealand. Its common names are ‘Horizontal Orbweb Spider’, ‘Silver Orb Spider’ and ‘Humped Silver Orb Spider’.

The first described specimen was misidentified by Koch in 1872 as a different northern Australian species (Leucauge granulata, the Roughened Silver Orb spider). Later in 1988, Davies (PDF) also misidentified the species. This is understandable as they are similar looking.


Appearance

This spider is relatively small being an average of 10 mm in length. The males are smaller than the females, as is the case with many spiders.* They have silver abdomens with black and yellow markings. Their leg colouration is generally a translucent yellow through blue with black bands. Their cephlothorax is normally buff-brown/orange to white.

Leucauge dromedaria [SILVER ORB WEB] Gordon's Bush, Whanganui, New Zealand 11-01-2018 (14)
Click to zoom in


Location

This spider is generally found hanging from its horizontal web over damp ground. We found ours near a marshy area at Gordon Park Scenic Reserve, Whanganui.

In New Zealand, these spider can be found across the North Island and at the top of the South Island. As for Australia, iNaturalist sightings show that they have been found on the east of lower Queensland and on the eastern parts of New South Wales. Archne.org.au explain the spider can be found ranging from Maryborough, Queensland south to Tasmania and New Zealand.

Click to zoom in


Behaviour and Adaptations

The Silver Orb Spider creates horizontal orb-webs from which it hangs. The spider’s silvery back faces towards the ground. This is the perfect camouflage as from beneath their web, their silvery body is easily lost against the bright sky. But, from above, their dark underside camouflages them against the dark foliage or soil.

They target flying insects as prey that are landing or ascending from plants and water surfaces found beneath their webs. Their diet consists of small insects such as moths, bugs, flies and beetles.

When disturbed the spiders drop instantly to the ground which makes getting close for a photograph particularly difficult!


*Interestingly, male spiders are often smaller than females due to the selection pressures associated with their dimorphic sexual behaviour. Males need to travel distances to find females. Many spiders utilise ‘Bridging’. This is an unusual mode of getting across large gaps in foliage. Researchers have shown that a spider’s ability to utilise the wind to carry a strand of web to their destination and then climb upside down along the resulting bridge, is associated with smaller size. Females are larger because this confers an advantage in generating offspring.

Click to zoom in


Want to read more?

Check out one of our other recent spider posts:

Zoomology - Polkadot Jumping Spider


References and Further Reading

Arachne Website – http://www.arachne.org.au/01_cms/details.asp?ID=2642
(Retrieved 30 March, 2018)

An Illustrated Guide to the Genera of Orb-Weaving Spiders in Australia – http://www.arachne.org.au/_dbase_upl/davies1988orbweavers.pdf
(Retrieved 30 March, 2018)

Brisbane Insects Wesbite – http://www.brisbaneinsects.com/brisbane_weavers/SilverOrbsSpiders.htm
(Retrieved 30 March, 2018)

iNaturalist Website – http://naturewatch.org.nz/taxa/368474-Leucauge-dromedaria
(Retrieved 30 March, 2018)

Science Daily Website, Why are male spiders small while females are giant – https://www.sciencedaily.com/releases/2010/08/100802221733.htm
(Retrieved 30 March, 2018)

T.E.R:R.A.I.N Website – http://www.terrain.net.nz/friends-of-te-henui-group/spiders/orbweb-spider-silver-orb-leucauge-dromedaria.html
(Retrieved 30 March, 2018)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s