All insects share the same basic mouthparts; mandibles for masticating food (chewing, crushing, tearing, cutting), maxillae for manipulating food, a lip-like labrum and a labium to assist manipulation of food during mastication. These structures are present in almost all insects but may differ according to their food requirements- for example the maxillae can be modified into a long sucking tongue for insects that drink nectar. 3 of the most common specializations are shown below.
Chewing (dragonflies, grasshoppers, beetles and various larvae): In carnivorous chewing insects, the mandibles have evolved to become more knife like, whereas in herbivorous insects the mandibles are flat and broad for chewing plant matter. In some insects the mandibles are modified to serve another function- this can be for defence (ants), sexual selection (stag beetles(, or nest building (paper wasps)
Piercing and sucking (hemipterans and mosquitos): These insects have evolved mouthparts that pierce foods enabling them to suck internal fluids- this could be plant or animal based liquids. In hemiptera the mandibles and maxillae are modified in to a proboscis which is sheathed within a modified labium to suck out plant fluid. In mosquitos the paired mandibles and maxillae form a stylet which pierces the animals skin where anti-coagulants in saliva is injected to the food and blood sucked out.
Siphoning (moths and butterflies): All but a few lepidopterans lack mandibles and the heavily modified maxillae is elongated to form a galea. This is coiled underneath the head when not in use, and extended into the corolllas of flowers in order to drink nectar.
Sponging (flies): The articulate labium possesses a sponge-like labellum on the end in order to channel liquid food upwards, after secreting and spreading saliva over solid food in order to dissolve it. Minute food channels cover the labellum’s surface, and the liquid is drawn up the tube by capillary action into the oesophagus.