Unearthing a larva is the cue for celebration during the annual survey of the chafer beetle population.
The survey takes place in mid-December and, this year, nine Department of Conservation staff and four AgResearch staff carried out the work.
They marked a grid across the reserve, and cores of earth 10cm in diameter and 5m apart were sampled.
Every sample was checked for larvae or beetles and the process took a full day, with about 700 samples taken.
Last year, no larvae were found but this year the survey team unearthed four larvae and two beetles.
"They look exactly like a grass grub," Invermay AgResearch scientist Barbara Barratt said as she held a larva for a photo, before returning it to its underground home.
The larva, annoyed at being exposed to the sun, took a few nips at its captor.
The population appears stable at present, but "contingency plans"- a mass rearing programme - is already under way in case the numbers wane.
Animal and plant pests at the reserve are controlled to protect the chafer habitat.
The larvae live underground and the beetles also live under the upper layers of sand during the day, coming out at night to feed on plants on the surface.
