They are NOT cockroaches or insects. They have seven pairs of legs,
huge eyes and very long antennae. Commonly seen on many of our rocky
or less. Body flattened sideways, seven pairs of limbs, can hop long
distances by flexing their long abdomens. Sometimes seasonally abundant
among seaweeds on many of ours shores.
Body enclosed in a two-part, hinged, hard translucent 'shell', somewhat
like a clam. Some can produce a blue luminous light when disturbed.
Commonly seen on our Northern shores, usually by their luminous sparks.