Chromosomes of Tetragnathidae (A–D) and Theridiidae (E–L). Pachygnatha sp. (2n♂ = 24, X1X20) A mitotic metaphase B late pachytene with positively heteropycnotic sex chromosomes C diakinesis D half of metaphase II, with slightly less condensed X chromosomes. Argyrodes cf. convivans (2n♂ = 21, X0) E mitotic metaphase F diakinesis with isopycnotic X univalent G half of metaphase II with despiralised acrocentric X chromosome. Argyrodes sp. (2n♂ = 21, X0) H mitotic metaphase I diakinesis with isopycnotic X chromosome. Theridion cf. purcelli (2n♂ = 22, X1X20) J diplotene, X1X2 associate on the periphery of the plate K metaphase II L anaphase II. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.