First, insects have compound eyes consisting of up to several thousand optical units called ommatidia, each with a single lens.
(insects; have; compound eyes consisting of up to several thousand optical units called ommatidia, each with a single lens) (compound eyes; consisting; of up to several thousand optical units) (up to several thousand optical units; called; ommatidia)
insects compound eyes up to several thousand optical units
have consisting called
compound eyes consisting of up to several thousand optical units called ommatidia, each with a single lens
of up to several thousand optical units
ommatidia