The Messenger of Allah ﷺ enjoined killing the two black ones (snakes and scorpions) while praying. (Using translation from Nasāʾī 1203)   

«أَنَّ رَسُولَ اللَّهِ ﷺ أَمَرَ بِقَتْلِ الْأَسْوَدَيْنِ فِي الصَّلَاةِ» قَالَ يَحْيَى وَالْأَسْوَدَاْنِ الْحَيَّةُ وَالْعَقْرَبُ