Insect Head Anatomy

     
Housefly Butterfly Mosquito
     The most distinguishing characteristic of an insect's head is the mouthparts.  They may be designed for chewing food, for sucking it or lapping it up.  The housefly uses its it's mouthparts are used for mopping; up liquid food.  The end of the labium functions like a sponge.  A butterfly sucks up its food through a part of the maxillae that forms a tube.  The mosquito also sucks ups its food.  All of its mouthparts, except the labium, form a needle-like tube called a fascicle. The ground beetle is a carnivore; it has large mandibles adapted for piercing and cutting prey. 
Beetle

Glossary

labrum - the so-called upper lip.
labium - the so-called lower lip.
palp - a segmented extension. 
labial palp - One of a pair of small feeler-like or antenna-like structures arising from the labium.
mandible - One of the anterior pair of mouthpart structures, commonly called jaws.
maxilla - one of the paired mouthpart structures immediately posterior to the mandibles.
maxillary palp - A small feeler-like or antenna-like structure arising from the maxilla; sensory in function.