Insect Mouthparts

Why would anyone other than an entomologist be interested in studying an insect's mouthparts? Well, the type of mouthparts will help to determine what insect order it belongs to. The type of mouthparts will also determine the type of damage left by the insect. Often when we arrive at the 'scene of the crime', the insect that caused the damage is long gone and we use the type of damage as a clue to determine which insect may have caused the damage. In addition, some insecticides are more effective against insects with certain types of mouthparts, so the type of mouthparts can affect control decisions. There are many types of insect mouthparts, but we will focus on the three most common types, chewing, piercing-sucking, siphoning, and sponging.

With piercing-sucking, the mouthparts form a tube which is inserted into a food source. Note the beak hanging below the head of the wheel bug. The food source could be a plant with herbivorous insects, or another insect with some insect predators.

Damage to plants caused by insects with piercing-sucking mouthparts would include stunting, yellowing, distorted growth, and honeydew (waste material from some sucking insects). Three orders of insects have this type of mouthparts: true bugs, thrips, and the Homoptera. Because the feeding occurs inside the leaf, these insects are less likely to be killed by insecticides that only coat the outside of the leaf. However, they are often very susceptible to systemic insecticides.

Chewing mouthparts are common in many different insect orders. Usually the most visible part of these mouthparts are the large mandibles on each side that move from side to side. Often there are noticeable, finger-like palps on each side of the mouth.

Many of the insect orders have chewing mouthparts, including beetles (Coleoptera), caterpillars (Lepidoptera), the Orthoptera, and termites (Isoptera). Insects with chewing mouthparts leave noticeable holes in leaves, wood, or fruit. Insecticides that lay on the surface of the plant may be effective as these insects often consume more of the surface area of plants than insects with piercing-sucking mouthparts.

Many moths and butterflies have siphoning mouthparts that are adapted to draw nectar from long-throated flowers. Unlike piercing-sucking mouthparts, these do not penetrate into the plant. When at rest, the tube is held as a coil under the head. A few moths have tubes that may be several inches in length when extended.

The other common type is that of the sponging mouthparts. Many of the flies, including the house fly, blow flies, and fruit flies have sponging mouthparts. Sponging mouthparts appear as a conical process with spongelike lobes at the end. This type of mouth is modified to lap up liquids. These flies often use enzymes to liquify the food before feeding.

Updated November 2005