In 2016, Coca-Abia and Romero-Samper found differences in syntype specimens between White's (1846) C. zealandica and Given's (1952) description, and revised the species name of the latter to C. giveni after Given.

Grass grubs belong to the holometabolous insect group, this means that they have a life cycle with four stages: egg, larva, pupa, adult.

On hatching larvae have a whitish/grey C-shaped segmented body, with a darker coloured head and dark brown jaws (mandibles).

The pupae start off the same creamy white colour as the larvae, but slowly turn to a dark brown during pupation.

They have a soft body and are generally shorter and thicker than the grass grub larvae, they grow to between 10–30 mm in length.

[8] New Zealand grass grub has an annual life cycle, taking typically one year under normal climatic conditions but can take up to two years in adverse weather such as drought or significant cold periods (this also includes periods where the soil moisture is very high), or due to a food shortage.

Females are the last to emerge from the soil, this leads to localized infestations due to them being unable to reach a significant distance before being mated.

Once they reach the appropriate depth, the grub empties its stomach and starts to form a smooth oval shaped cell.

The grass grub populations usually increase in a 3-5 year cycle before crashing, usually due to a buildup of disease in the soil.

[9][10] The larvae of C. giveni tend to feed on fine roots of pasture plants like perennial ryegrass (Lolium perenne) and white clover (Trifolium repens).

If there is a concentrated group of beetles flying in one area, there is potential to defoliate seedling crops and fruit trees.

Great black backed gulls (Larus marinus) prey on the grubs especially in areas undergoing cultivation.

Amber disease is a chronic infection of the stomach of grass grub larvae, and is caused by two strains of bacteria, Serratia entomophila and S. proteamaculans.

Once these pathogenic bacteria have been ingested, the infected larvae stop eating within 2–5 days, and gain an amber colouring due to the stomach emptying, and the levels of major digestive enzymes (trypsin and chymotrypsin) in the mid-gut decreasing.