Begin tunneling under known defensive positions being taken up by beetles.  

Teams of warriors are to burst up from beneath the beetles before dragging them under and to their deaths. All offensives are to be overseen by Princes augmented with warrior-like traits.

Suggestion: perhaps a small, powerful pincer of the front most leg of warriors would allow them to tear away beetle shells.
 
Increase overall strength of warrior drones.

Study how beetles manage to remain unaffected by rain.