The Net Casting Spiders (Deinopidae)

Meet Deinopis Macleay, 1839. 

Male. Photographed in Chongwe District, Lusaka Prov., Zambia, November 2016, using Olympus E-420 and 3 KOOD lenses. 

Deinopis is the more iconic of the two genera of Net-Casting Spiders, distributed throughout the warmer regions of the world; it lends its name to their family (Deinopidae), and is the source of another common name for the family - Ogre-faced Spiders - and, locally at least, species of this genus are physically much larger, and difficult to overlook. This impressive male, found wandering on a driveway on a hot, humid night, had legs that spanned over 5cm.

To put this in context, his legs are very long; unusually long, you might think (if you are used to thinking about these things) for a spider that neither lives in caves (where anything and everything has a license to have very long legs) or live in a web





But this little Kangaude (Chewa - spider) does build a web. To those who know a little about spiders, this doesn't really resolve much: while his legs make slightly more sense, now, his eyes become something of a puzzle: of the other spiders blessed with such large and conspicuous peepers, most belong to either the Jumping Spiders (family Salticidae) or the Wolf Spiders (family Lycosidae); the vast majority of which are active, free-living predators, which use their eyes to see, hunt and capture prey - or, in the case of most jumping spiders - to communicate via semaphore.

To explain all of this, we have to turn to Deinopis' smaller and more abundant relative - and the only other genus in the family - Menneus Simon, 1876 - for a practical demonstration: 

Photographed in Chongwe, Lusaka, Zambia in April 2015. 

As already mentioned, one of the common names for this family of spider is Net-Casting Spider (and I will eventually find the direct Chewa translation for that, in theory); and they do precisely that; they wander around in search of a crossing point of nocturnal insects to wander through, and then, suspended above it by a simple thread, they spin an entire web between their (very long) front legs, and they wait.

And they wait.

Eventually something wanders past, and, seeing the movement, they whip down the net and voila, pre-wrapped meal - and a unique method of hunting that needs both a web and excellent vision.

Menneus - note the smaller eyes and the abdominal 'hump'. 

It is worth noting that Menneus' vision isn't quite like Deinopis'; they are probably most easily identified, in fact, by lacking the massive enlargement of the posterior median eyes seen in Deinopis; their eyes are still larger, on the whole, than those of most web-spinning spiders, but if it wasn't for their extraordinary webs, and the curious protuberances from their abdomen (earning them the alternative names of Camel-backed Spiders and Hump-Backed Spiders), they might be mistaken for free-living nursery-web spiders (family Pisauridae). 

Although identification to genus for this family is extremely easy - especially now that Avella and Avellopsis have been shoehorned into Menneus - you'll notice that I haven't listed a species name for either of our two guest-stars; although none appear to be recorded specifically from Zambia, a number of species are recorded from neighbouring countries and the wider region (see the World Spider Catalog page on the family); and - as the spiders are inconspicuous, nocturnal and easily overlooked - there is every chance that these do not belong to described species at all.

So I'll get back to you on that.