The thermal conductivity and diffusivity of the dragline silk of the Nephila (N.) clavipes spider has been characterized by one research group to be 151-416 W m(-1) K-1 and 6.4-12.3 x 10(-5) m(2) s(-1), respectively, for samples with low to high strains (zero to 19.7%). Thermal diffusivity of the dragline silk of a different spider species, Araneus diadematus, has been determined by another research group as 2 x 10(-7) m(2)s(-1) for un-stretched silk. To improve measurement reliability and repeatability and resolve the orders of magnitude discrepancy between the two different measurements, this paper measured 13 un-stretched dragline silk samples of the N. clavipes spider with different lengths using the same electrothermal technique as the first group but with a much higher vacuum level and an improved heat transfer model. The measured thermal conductivity is 1.2 W m(-1) K-1 and thermal diffusivity is 6 x 10(-7) m(2) s(-1). The measured thermal diffusivity of the N. clavipes spider silk is in the same order of magnitude as that of the diadematus spider but is 1/100-1/200 of the value by the first group. The measured thermal conductivity is 1/150-1/400 of that measured in literature. The discrepancy between this research and the first group may reside in the vacuum level and the improved heat transfer analysis. The difference in thermal diffusivity measurement between the current research and the results of the second group may be because of different species. (C) 2014 Elsevier Ltd. All rights reserved.