It's what's known as a bioluminescent burglar alarm, and just like the alarm on your car or your house, it's meant to cast unwanted attention onto the intruder, thereby either leading to his capture or scaring him away.
Nazývá se to bioluminiscenční poplašný systém. A podobně, jako u alarmu na vašem autě či domě, smyslem je zaměřit pozornost na vetřelce, s cílem jej dopadnout nebo vyplašit.