Many insects are unable to cut and chew solid food, and only eat only liquid food. The strong, sharp mandibles, maxillae and other mouthparts of sucking insects have changed into styluses. These long mouthparts form a tube used to suck up liquid food.
In general, the mouth of a sucking insect works like a pump. Different groups of sucking insects are characterized by the number of styluses, their arrangement and the way they work.
Licking-sucking insects
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Some sucking insects, like houseflies and fruit flies, are classified as sponging insects. Their mouth looks like a sponge at the end of a short trunk called a proboscis. Houseflies generally eat liquid food, but they are also capable of liquefying solid food with their saliva. A fly can fold up its proboscis behind its head when not in use. |
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Butterflies are sucking insects. Their mouthparts include labial palps and elongated maxillae. The maxillae are joined together to form a long trunk. When at rest, this trunk is rolled up behind the butterfly’s head; when unrolled, it looks like a straw. Butterflies are well equipped to suck nectar from flowers and juice from fermenting fruit. |
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There are some exceptions. Adult moths of some species, such as the luna moth, have atrophied mouthparts and are unable to eat. They live on food stores accumulated in their caterpillar stage. Some others (some noctuidae) are piercing-sucking. |
