Mr Harris, the Otago Daily Times' Nature File columnist, moved from Wellington to become a curator at the museum in 1974.
Recent Dunedin winters have been much milder than in the past, he said.
Dunedin's five species of ants were usually inactive throughout the winter, but this year three species had continued foraging, he said.
A member of the public yesterday reported seeing increased ant activity, and recently found two ant nests on adjoining central city properties.
Mr Harris said the city's ant species posed few risks for householders and tended not to invade cupboards.
In Dunedin this year, he had seen ants nesting under stones and under concrete paths in winter, and many more ants than usual walking along ant trails, often at the edge of paths at suburban houses.
He had also received reports of many more common and German wasp queens - Vespula vulgaris and Vespula germanica - overwintering in the city than usual.
Ryan Hiko, who lives in Hagart-Alexander Dr, Mosgiel, recently sent Mr Harris a photograph showing 16 of about 60 common and German queen wasps, caught in a wasp trap and a glass of fruit juice left outside, in late September or early October.
Mr Harris said large numbers of fecundated queen wasps had been found throughout Mosgiel and Dunedin, hibernating in masses of up to 80 individuals.
"In previous years they have not been found in these exposed situations and never before in these numbers," he said.
A resident of Islington St, Northeast Valley, reported finding 77 new queens that had overwintered in vegetation growing beside the walls of his house.
