These rotund little bugs are not known for rapid running or flying. They seem like easy pickings for a predator. Evolution must have provided a 'catch'. The 'catch' is you need to win over 'minders' by addicting them to your 'urine'! Many types of bugs produce a carbohydrate and sugar rich solution from their rear ends that ants find irresistible - English speaking humans call it 'honeydew'. In order to protect their little 'dealers' they will attack any threat. As to why they were not present when this photo was taken....who knows....maybe a change of shift;-}!