maximum 520: average 350 MJ/m^3
||Bark spider Caerostris darwini
||Mammola S, Michalik P, Hebets EA, Isaia M. Record breaking achievements by spiders and the scientists who study them. PeerJ. 2017 Oct 315:e3972. doi: 10.7717/peerj.3972 p.18 6th paragraphPubMed ID29104823
||Agnarsson I, Kuntner M, Blackledge TA. 2010. Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb spider. PLOS ONE 5(9):e11234 DOI 10.1371/journal.pone.0011234 AND Guinness World Records (GWR). 2017. The Guinness World Records. Available at link guinnessworldrecords.com (accessed 4 October 2017) PubMed ID20856804
||P.18 6th paragraph: "Strongest silk—520 MJ/m^3. The Darwin’s bark spider, Caerostris darwini Kuntner & Agnarsson (Araneidae), produces the toughest known spider silk (primary source GWR, 2017, see also “Largest web”). Tensile testing has shown that certain threads may reach the toughness of 520 MJ/m^3 (average = 350 MJ/m^3). The silk of Caerostris darwini is therefore over 10 times tougher than Kevlar [="a heat-resistant and strong synthetic fiber, related to other aramids such as Nomex and Technora"-wikipedia](primary sources Agnarsson, Kuntner & Blackledge, 2010, GWR, 2017) (Fig. 3E)."