http://www.kashrut.com/articles/Bugs_in_Lettuce/The Prohibition of Eating InsectsThe Torah prohibits the consumption of many types of sh’ratzim , such as insects, worms, and other “creepy crawlies”. Specific prohibitions govern those that live in rivers and lakes, those that creep on the ground, and those that fly in the air. The prohibition against eating forbidden insects is so expansive that the Talmud (Makos 16b) notes that eating even one whole insect may occasion multiple transgressions. According to the P’ri Chodosh , the reason for this extraordinary compounding of prohibitions is the ubiquity of insects and the resultant ease by which one may easily transgress this prohibition. One must, therefore, exercise great care to avoid eating foods that contain insects and thereby transgress these prohibitions. As we shall see, however, not all “insects” are created equal.
The term “She’retz ” refers to small, slithering creatures. In the case of terrestrial Sh’ratzim , these include small animals, such as mice. The short legs of such animals are not readily noticeable as they move, rendering their movement akin to slithering. Even small mammals, such as mice, fall into this category. Fortunately, we are not often faced with the problem of mice in our food supply. Other creatures that are considered Sh’ratzim , notably insects, worms, and crustaceans, however, do infest food. As we shall see, in many cases the Torah prohibits us from eating foods that may contain prohibited Sh’ratzim .
(It is also important to note that while the technical term “insect” is a precise scientific term referring to a specific class of arthropods, in discussing the prohibition of sh’ratzim when we use the term “insect” it is in its non-technical sense. For the purposes of our discussion, the word “insect” connotes any type of small, prohibited organisms – insects, crustaceans, and worms.)
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Microscopic Insects. Concerns over sh’ratzim in vinegar, however, do afford us another important Halachic insight. With the development of the microscope, people realized that vinegar eels were but a miniscule part of the broad microscopic flora found in vinegar – and virtually all other liquids. The Halachic ramifications were obvious. If, indeed, magnifying optics revealed “bugs” in virtually all foods and liquid – or, for that matter, the air – how is one Halachically permitted to consume them? The answer to this question was unequivocal. All Poskim have concurred that Halachic requirements relate only to what can be seen by the unaided human eye. This approach has countless Halachic applications, from cracks in letters of a Sefer Torah to miniature scales on fish to minor blemished on an Esrog . From a Halachic standpoint, what cannot be seen by someone with average eyesight has no Halachic standing.
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Approaches to dealing with Miyut ha’MatzuyBasing himself on a ruling of the RaShB”A , the Ramo (Y.D. 84:8) rules that once a fruit is considered in the category of Miyut ha’Matzuy one is required to inspect each fruit or vegetable individually (he specifically states that one cannot rely on the checking of the majority). As such, many common fruits and vegetables should not be eaten unless thoroughly inspected. [A definitive listing of the status of specific fruits and vegetables at any one time or place is beyond the scope of this article.] However, three additional factors may serve to mitigate this requirement.
The first involves the concept of Nireh l’Ayin – the requirement that a prohibited insect be visible to the unaided eye. Should the insect be so tiny as to be imperceptible to a person with normal eyesight, it would pose no Halachic concern. If it can be seen and identified by a person with normal eyesight, albeit only under careful inspection, it would be prohibited. One situation, however, poses an interesting question – if the presence of an insect can be noticed but cannot be identified as an insect without further magnification. Some authorities posit that although it may look like a spec of dirt, it nevertheless qualifies as a “visible” – and prohibited – entity. Others, however, argue that it cannot be considered a “visible” insect unless it can be so identified. Again, one should follow his Posek in this matter.
A second mitigating factor involves the concept of Bitul (nullification). Under normal circumstances, mixtures containing forbidden components are permitted if the offending material is less than one part to sixty (about 1.6%) of the whole mixture and not intentionally added. One could therefore argue that since levels of infestation are generally below that level, most produce should be permitted without any further concern. There are two problems with applying the concept of Bitul to vegetables, however. Most authorities rule that since an inspection can identify an insect mixed with vegetables, they are not considered a true “mixture” – a Ta’aroves – subject to the rules of Bitul . In addition, even if it were considered a Ta’aroves , insects generally have the Halacha of a Beryah – a “complete” item, and a Beryah is not considered Batel regardless of its ratio in the mixture.