giant predacious diving beetle eggs

[hardshell]

i have some predacios diving beetles (2 males, 3 females) and i havent seen them mate. but females are keep making holes on my banna plant (which has thick roots i really recommand them. so my beetles are keep making bite marks on the roots but when i cutted one of the roots i didnt see any eggs or larvae. is this eggs laying behavior or what? i clean my cage once a week so i think its hard for me to see any hatched larvae. how do u guys make the water so clean? without filters thanks for reading

 

[Lucanus]

Depending on species you have, this behavior may or may not be egg laying behavior.

Beetles in genus Dytiscus are known to lay their eggs on the surface of plants and rocks while beetles in genus Cybister are known to drill holes on plants and oviposit there.