The mouthparts of insects, mites and slugs and snails have adapted over time to better suit the food source and feeding style of the organism. Mouthparts differ from insect to insect and the damage that they cause is useful in the classification and identification of the pest. Being able to identify the type of damage caused by the various types of mouthparts also helps differentiate insect damage from mite damage and will help you determine how to control the pest.
There are two main categories of mouthparts:
Chewing mouthparts are the most primitive type of mouthpart and are often referred to has mandibulate mouthparts. There are many different variations on the basic type of chewing mouthparts depending upon what the insect feeds on. Let's have a look at the basic structure by using a diagram of a grasshopper to demonstrate.
Examples of insects with chewing mouthparts are grasshoppers and beetles, and various caterpillars or larvae of moths and butterflies.
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Taking a closer look at the damage caused by a particular organism gives us a clue as to which kind of insect or mite has caused the damage. The signs of damage that an insect or mite with piercing-sucking mouthparts has caused, looks very different from the feeding pattern of an insect with chewing mouthparts. Chewing mouthparts result in parts of the plant being chewed or torn off. It can be easily identified by holes in the leaf or chewed edges.
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Non-chewing mouthparts are modifications of mandibulate mouthparts and are used for 'sucking' up liquids or rasping across the surface of the leaf.
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Piercing and sucking mouthparts are modification of the mandibles and maxillae, which are elongated and modified to form a proboscis for piercing plant tissues. The insect pierces the surface of the plant and sucks out the sap from within. This action also removes the green chlorophyll from the plant.
Examples of insects with piercing-sucking mouthparts include; aphids, leafhoppers, mealy bugs and fleas.
Rasping and sucking occurs when the insect or mite scrapes off the leaf surface and sucks up the fluids from the top layer of cells. This causes the leaf to turn a silvery colour.
Examples of pests with rasping-sucking mouthparts include thrips and mites. The damage caused by thrips and mites looks very similar.
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Insects with piercing-sucking mouthparts like aphids pierce parts of their host plant, causing the affected area to become brown or resulting in wilt or a tumour-like growth. Pests with rasping-sucking mouthparts like thrips and mites remove the top layer of cells and suck out the cell contents, causing the leaf to look a silvery or bronze colour. With both these types of damage there is never any part of the plant missing.
