Various types of insect mouthparts

Piercing-sucking mouthparts differ primarily in the number and arrangement of the stylets (needle-like blades) and the shape and position of the lower lip of insect mouthparts, termed the labium. Often, what is called the proboscis of an insect with piercing-sucking mouthparts is an ensheathment of several components such as the labrum, stylets, and labium. For example, mosquitoes have a proboscis composed of six stylets (two mandibles, two maxillae, the hypopharynx, and labrum-epipharynx), ensheathed in an elongated, cylindrical labium (B). Horse flies, deer flies, black flies, and biting midges basically have the same type of mouthparts: blade-like (A). Most of the stylets are flattened compared with those found in mosquitoes. The mandibles are flattened and move transversely in a scissor-like fashion, and the maxillae are thrust in and out of the wound, causing pooled blood in the host's tissues. In tsetse flies, teeth on the labellum aid the labium for penetrating the skin (C). Movements of the fly's head further enable the labium to gain access to capillaries in the skin. Members of the insect order Hemiptera, or true bugs, have a hardened, three-segmented beak that they insert into plants or prey for feeding or human/animal hosts for blood feeding (E).

Other arthropods such as spiders, mites, and ticks also have piercing-sucking mouthparts, but the structures are derived from different morphologic features than those of insect mouthparts. Mites and ticks have a head-like gnathosoma for feeding. The gnathosoma consists of mouthparts and palps and forms a tubular structure for obtaining food and passing it into the digestive tract. The cutting-piercing mouthparts of mites and ticks are called chelicerae. Chelicerae may cause tearing of skin, as in the case of scabies mites, or piercing, as in the case of chiggers. In ticks, there is an additional anchoring hypostome, which is a very prominent structure and bears teeth on its ventral surface. The true bugs, such as bed bugs, kissing bugs, and assassin bugs, have the labium formed into a prominent three- or four-segmented cylindrical proboscis (E).