Male and female biases in offspring production hold an intriguing question for biologists as an equal sex ratio is long considered an evolutionary stable strategy. In line with this, examples of biased sex ratios can be found in nature, though they are relatively rare. One such example is the spider genus Stegodyphus which is characterized by both temporarily (subsocial) and permanently social species. With increasing sociality these species exhibit a more limited male dispersal and consequently elevated levels of inbreeding. Besides these marked differences in relatedness between reproducing individuals a consistent pattern of sex ratio variation is observed with subsocial species producing equal amounts of male and female offspring while social species are highly female biased. This is interesting from a mechanistic point of view as this contradicts the expected equal sex ratio, predicted by a sex chromosome based sex determination. Our aim is to pinpoint the exact reproductive stage of bias occurrence (sperm production, egg stage,…) through the use of different molecular techniques such as flow cytometry, next generation sequencing, FISH...