Studies on Invading Insects and Mites of Dry Milk Cans Set in Several Homes

Abstract

Insects and mites invading into four types of milk powder cans and changes of water content of their cans were investigated after setting them for two weeks in thirty homes which were five kitchens of apartment buildings, five of houses and five of stores (food-stores or restaurants) in both of the downtown and the suburbs. Four types milk powder cans were; 1) A can closed by a metal screw cap. 2) Closed by a polyethylene-cap. 3) Ccovered loosely by a polyethylene-cap without being closed and fixed by vinyl tapes on both sides. 4) Closed by a cap of which one-fourth part was cut off. We tested in summer, autumn and late autumn in 1974.
It was found that water content of milk powder was highly correlative with the number of kinds of invading insects and mites. The numbers of insects and mites increased more in cans set in moist places. Also it was found that cans closed by polyethylene-caps were less invaded by insects and mites than cans closed by metal screw caps because the latter cans had more openings than the former.
There were no statistical significant differences between downtown and suburbs, among apartments, houses and stores, and among three tests done at three seasons.