A praying mantis has 5 eyes...you can see the three others on the crown of its head .
A mantis has two massive compound eyes. But they also have three smaller eyes located on the middle of their head. Those eyes are used for detecting light while the big eyes are for seeing movement and having depth vision.
This mantis below is not from Hong Kong, it is a Malaysian Leaf mantis, and whilst I was taking its portrait this small ant crawled across one of its eyes.