The Question of Tiny Insects
In order to understand the entire scope of the prohibition of shratzim (worms and insects) and the extent to which one must make an effort to check food for them, it is necessary to explain the basic dispute regarding tiny bugs.
Ordinary Torah students think that the law of tiny shratzim is simple: what a person can see is forbidden, and what he cannot see with his naked eyes, but only with the help of a magnifying glass or a microscope, is permitted.
This is indeed what several Achronin wrote (Binat Adam 34:49; Aruch HaShulchan 84:36; Igrot Moshe, Y.D. 2:146; Yibeah Omer 4, Y.D., 21).
This is indeed what several Achronin wrote (Binat Adam 34:49; Aruch HaShulchan 84:36; Igrot Moshe, Y.D. 2:146; Yibeah Omer 4, Y.D., 21).
According to this, presumably, one needs to know how small an object a person can see, and in view of that, determine the halakha. However, this definition is not sufficient, because eyesight varies from person to person, and also depends on the color of the insect and the background on which it is situated. A person with good eyesight can see on a white background large black bacteria the size of five hundred microns (0.5mm), however, when the color of the insect is similar to the background on which it is situated, even if it is ten times larger, one will not be able to see it, and only laboratory workers will possibly be able to see it.
People with good eyesight cannot always detect even a two-millimeter insect, however, when it is pointed at, they are able to see it. In other words, seeing the tiny insect depends on several factors: a) its size, b) the quality of one’s eyesight, c) the color of the sheretz (insect) and its background, d) recognition of shratzim, and e) how it is situated, for if it is crawling, it is easier for it to be seen.