Arachnids (IMAGE) University of Wisconsin-Madison Caption In a study of arachnids like the common house spider, University of Wisconsin-Madison researchers found that a gene known as Sp6-9 that is normally involved in telling developing insect and arachnid embryos where to grow legs has also been coopted in arachnids to properly form their heads, or the segments of the animals where the first and second walking legs emerge. Without Sp6-9 (right panel), the legs are shortened and the head does not develop normally. Image courtesy of study authors Emily Setton and Prashant Sharma Credit UW-Madison Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.