Our Observation of the Week is this Twig Spider (genus Poltys) egg sac, seen in Singapore by @nickybay!
A few weeks ago, David Ringer (@djringer) messaged me on iNat and suggested we feature a gorgeous spider egg sac observation from Nicky Bay (@nickybay) as Observation of the Day, which I happily did. The extra attention gave the community some clues as to which spider might have constructed this silken puffball.
From David:
I like looking through the orbweaving (Araneoidea) and unclassified spiders from tropical and subtropical Africa, Asia, and Australasia. Several times over the last few years, I'd noticed photographs of apparent orbweaver (Araneidae) egg cases covered in hot pink silk threads, usually with a “tail” or “ribbon” of silk decorating the construction…I had no idea what was making the pink ones, and apparently no one else on iNaturalist did either.
One possibility was the genus Poltys, a genus of nocturnal, highly cryptic (and often spectacular!) twig- and dead leaf-mimics. However, I didn't find any compelling images of their egg cases. This genus is restricted to Africa, Asia, and Australasia, and although its relationships within the family Araneidae are not very well studied, Scharff et al. (2020) indicated they may be related to Eriovixia and Bijoaraneus, two other orbweaver genera from the same broad region.
“I've been fascinated by the lesser-seen details in our microfauna and used to spend some time visiting macro photography forums,” says Nicky. “So when my wife got me a camera, I bought a macro lens the next day. To me, macro photography is like a window to an alien world right under our noses.”
Nicky now goes on weekly night hikes with a few friends to find and photograph tiny wildlife and “[we] get excited whenever we find something new. Taking photos is like catching Pokemon. I also do short expeditions around Southeast Asia for this.”
It was on one of these recent hikes that Nicky’s friend spotted the colorful egg sac you see above.
I've seen somewhat similar egg sacs before that belonged to Araneidae, but nothing quite like it. Given the size of the egg sac, the spider must have been large enough to be familiar to us.@djringer triggered the discussion and I think you've seen the rest! The vital clue was provided by our friend in Japan (sasagani_ya) after a repost (arachnonaut) of the Observation of the Day on Twitter/X.
“[Those comments] led me to this paper,” says David, “which describes egg cases of P. stygius as being ‘overlaid with rose pink silk.’ So it now seems that Poltys species of the P. illepidus" species group (which includes P. stygius) are responsible for creating these gorgeous egg cases. I love the idea that a nocturnal, very camouflaged spider would create something so showy and fabulous.
Nicky (above, with an experimental “bazooka” macrophotography set-up) has an archive of thousands of photos, and has co-authored "Borneo Spiders: A Photographic Field Guide".
I am not a researcher, but my interests lie in spiders, isopods and lantern bugs (Fulgoridae). I am also part of the organising committee for the 9th Asian Conference of Arachnology in Laos this year. Excited to meet the arachnological community and post observations from Laos (think eyeless spiders).
I started using iNaturalist in 2022 after running a macro photography workshop in Ecuador where the microfauna was unfamiliar to me. One of the participants was a heavy iNaturalist user and encouraged me to try it out. Since then, I've been using iNaturalist as a catalogue of my findings. The AI suggestions are pretty accurate for certain taxon groups but it gives me a decent hint about 80-90% of the time so that I can dive into the corresponding literature to check. I like to organise my observations taxonomically so iNaturalist is perfect for this (except that I am still waiting for the feature to sort observation listings taxonomically!).
For his part, David encourages iNat user to annotate spider observations for eggs and constructions, because “unlike Lepidoptera and some other groups, spiders are very poorly annotated here on iNaturalist, which makes it hard to find good images of egg cases and other structures they create. There's a lot left to discover!”
(Photo of Nicky by Kelvin Dao)
- spider egg sacs are remarkable works of construction, here’s some footage of an Argiope making one.
- David and @michael-gasteracantha spotted an undescribed spider seen by @ivanovdg19 and it’s a past Observation of the Week!