frow what was Lexx bred?

While your stock Insect Civilization insect can’t shoot the same way the Lexx shoots, it probably CAN shoot “sheets of pure energy” similar to the Foreshadow and the hand weapons routinely seen in the light universe.

Why?

Because HDS had the power to emanate these “sheets of pure energy” directly out of his body. This surely must be derived from the Insect essence within him, and therefore be an inherent capability of the Insects themselves.

Why didn’t we see the Giga Shadow shoot these sheets?

Maybe because it was “prematurely reborn” and not fully awake before it got sucked into the fractal core.