Form & Function the Insect Head

Definitions

Mouthparts - labrum and 3 sets of paired and modified appendages. Listed from the most anterior to most posterior.

1. Labrum - plate (sclerite) that serves as upper lip in insects with chewing mouthparts. Helps to pull food into the mouth.
2. Mandible - paired appendage of the 4th body segment that becomes the 1st pair of mouthparts, analogous to jaw. Used to chew, cut, and tear food, to carry things, to fight, and to mold wax. Move from side to side rather than up and down.
3. Maxillae - 2nd pair of feeding appendages, used for food handling and sensing. More complicated than the mandibles but working in the same manner.
4. Labium - fused, 3rd pair of feeding appendages, analogous to lower lip. They function to close the mouth below or behind. Evolved from paired maxillae-like structures that are fused along the center line.

   ---

Generalized Insect Head with Chewing Type Mouthparts

Structure of mouthparts gives clues to food type and insect habits

  Mandibles Types

Modifications of Insect Mouthparts

Sponging - Found in adults of specialized flies. During feeding the proboscis (modified labium) is lowered and salivary secretions are pumped onto the food. The dissolved or suspended food then moves by capillary action into the pseudotracheae (sponge) and is ingested. There may be sharp teeth on the pseudotracheae to rasp flesh and draw up blood. The labella is the fleshy distal end of the labium that functions as a sponge-like organ to sop up liquids.

Siphoning - Moths and butterflies. When feeding the proboscis is uncoiled and extended.Nectar is sucked upinto the mouth or oral cavity. The proboscis is a modified maxillae.

Piercing-Sucking - Found in a variety of insects, such as herbivorous and predacious bugs and mosquitoes. Mandibles and maxillae are formed into stylets which are enclosed by the labium. Once the stylets penetrate, a secretion is injected to dissolve tissue, act as a toxin in predacious species, or as anticoagulant for mosquitoes.

Chewing-Lapping - Adult honeybees and bumble bees. Mouthparts are modified to utilize liquid food, honey and nectar. A central "tongue" is used to draw liquid into the body. The mandibles are not used for feeding but function to cut floral tissue to gain access to nectar, for defense, and for manipulating wax.

top of page
Entomology  home page
Entomology  topics list

Last updated Dec. 30, 2000
Gary Brewer