Article and images by Michael Mills, community conservation officer, Sunshine Coast Council
What big eyes you have…
Net casting spiders are a group comprising 2 genus, Deinopis (pictured in this article) and Menneus. Menneus have smaller eyes than the Deinopis genera, being the main difference. Net casting spiders, sometimes referred to as ogre-faced spiders, are an interesting group of spiders that are medium sized, stick like, and semi-nomadic.
They do not build a traditional web to catch their prey and live their life. Members of these genus have been shown to have superior night vision to cats and owls. Their eyes are capable of focusing light more effectively via a large, light-receptive retinal membrane. This membrane is damaged by sunlight and deteriorates each morning and regenerates in the evening.
Despite their amazing eyesight, it’s the way the net-caster hunts that gives them their name. They build a small rectangular net of entangled silk threads, achieving an almost woollen material.
The net caster identifies a pathway used by prey and suspends itself above the target area. It does this by using a safety line with supporting and anchoring lines to hold itself in position, even in windy conditions. The net caster does not use silk detection lines to determine if it is time to spring their attack. They secrete white droppings down onto the surface below them, which they can easily see in the dark. When prey walk over the top of these the spider knows to drop and ensnare the unsuspecting prey. Unused nets are sometimes stowed on nearby foliage for the day or may be consumed by the spider.
Net-casters are not considered aggressive and in fact are quite timid, and do not have venom that is toxic to humans. They are often found in forest habitats, generally sclerophyll to rainforest vegetation types. These photos were taken around the Buderim area, where I have noted the species on several occasions within reserves and in my own garden. Keep an eye out for these spiders around your yard, or when you are out in your local area.