Fundamentals of Entomology

Insect mouth parts

MOUTHPARTS
Just as insects take on many different forms, they also possess a variety of different mouth types, each of which can be grouped under one of two main categories: chewing (mandibulate) and sucking (haustellate).
• Mandibulate mouthparts, like the ones illustrated below, are believed to be the most primitive. All others, including those categorized as haustellate, are presumed to have evolved as modifications of this basic type.
• The five primary parts of the insect "mouth" are:

  1) The clypeus
  2) The "upper lip", or labrum
  3) Two "jaw-like structures", or mandibles
  4) The maxillae (sing. maxilla)
  5) The "lower lip", or labium

• The maxillae and labium are divided into various substructures, which include the galea, paraglossa, glossa, and the maxillary and labial palps.  

• Haustellate mouthparts are primarily used for "sucking up" liquids, and can be broken down into two subgroups: those that possess stylets and those that do not. Stylets are needle-like projections used to penetrate plant and animal tissue. Examples of insects with stylets include Hemiptera (true bugs), Diptera (flies), and Siphonaptera (fleas).

• Some haustellate mouthparts lack stylets. Unable to pierce tissues, these insects must rely on easily accessible food sources such as nectar at the base of a flower. One example of nonstylate mouthparts is the long siphoning proboscis of butterflies and moths (Order Lepidoptera). Although the method of liquid transport differs from that of the butterfly's proboscis, the rasping-sucking rostrum of some flies is also considered to be haustellate without stylets.