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SYNOPTIC DESCRIPTION OF THE SUBPHYLUM HEXAPODA

SYNOPTIC DESCRIPTION OF THE SUBPHYLUM HEXAPODA (LATREILLE 1825)

EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> PROTOSTOMATA> ECDYSOZOA> PANARTHROPODA> ARTHROPODA> HEXAPODA
HEXAPODA LINKS

Introduction

Hierarchical Classification

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Ruppert and Barnes (1991), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000).

I. SYNONYMS: insects, bugs, arthropods.

II. NUMBER: >1,000,000 species known.

III. PHYLUM CHARACTERISTICS:

  • A. Structure
    • Symmetry: Bilateral with head (5 fused segments with acron (text with tooltip) Acron (n.) is the preoral part of the insect head, the 'summit' of the body. and oral region with mouthparts formed by modifies legs), thorax (3 segments, each with a walking leg; most adult insects with 2 pairs of wings), and abdomen (11 segments with considerable fusion in some groups) without walking legs.
    • Body Cavity: True coelom reduced and absent in adults. Haemocoel (text with tooltip) A haemocoel is the primary body cavity of arthropods and related organisms. It is characteristic of organisms with an open circulatory system in which the blood 'circulates' in a large open sinus that surrounds the organs. the only body cavity.
    • Body Covering: Covered by chitinous exoskeleton.
    • Support: Hardened exoskeleton.
    • Digestive System: Food tube simple. Mouth at anterioventral end bordered by upper lip (of epistome (text with tooltip) The epistome is a part of the head in different arthropods. It is the region behind the mouth in insects and between the antennae and the mouth in crustaceans. It also is the preoral lobe of phoronids. and labrum (text with tooltip) The labrum is the anterior-most lip of arthropods and the outer margin of some gastropod shells. ) and lower lip (of maxillae (text with tooltip) Maxillae (maxilla, sing.) are the paired lateral jaw-like appendages on the head or cephalothorax of arthropods; the upper jaw in vertebrates. or labium), and has mandibles (text with tooltip) Mandibles are the lower jaws of vertebrates. In arthropods mandibles are modified legs that serve as biting mouthparts. . Hypopharynx. Food tube of three regions: fore- (text with tooltip) The foregut (also called the stomodaeum) is the anterior portion of the gut that is lined with ectoderm. , mid- (text with tooltip) Midgut (also called mesenteron) is the mid portion of the digestive tract, lined with endodermis and derived from the archenteron. , and hindgut (text with tooltip) The hindgut is the posterior portion of the gut that is lined by ectoderm. . Anus terminal.
    • Circulatory System: Open. Haemocoel of blood sinuses with a dorsal heart. No respiratory pigments in the plasma .
    • Locomotion: Each segment bears one pair of unbranched, jointed legs. Lost or highly modified in some. When present, the first leg segment is the coxa ( coxae (text with tooltip) Coxae (coxa, sing.) are the joints of insect legs closest to the body. )
    • Excretory System: Malpighian tubules (when present) discharge into gut at junction of mid and hind- gut.
    • Nervous System: Circumesophagial brain and a double, ventral nerve cord with segmental ganglia. The head capsule (fused segments at the anterior end) have simple and compound eyes (text with tooltip) A type of eye characteristic of most arthropods. It is made of many individual simple ommatidia (ommatidium, sing.), each of which is like a simple eye with a lens and light-sensitive cells. as well as antennae, sensory hairs.
    • Endocrine System: Complex, with hormonal control of sexual reproduction, development, growth, and communication.
    • Respiratory System: Tracheal (text with tooltip) Trachea (tracheae, pl.) is the windpipe of vertebrates, the air-filled tubes in most arthropods. system, usually paired spiracles (text with tooltip) Spiracles are openings on the abdominal segments of insects and body segments of myriapods through which air enters the tracheal system. It also is a small circular gill slit in some chondrichthyes. at each segment.
  • B. Reproduction:
    • Reproductive System: Dioecious (text with tooltip) Dioecious organisms have separate male and female individuals. . Gonads (text with tooltip) Gonads are sex glands in animals. Ovaries produce eggs and testis produce sperm. one to many. Fertilization internal (by spermatophores (text with tooltip) A spermatophore is a gelatinous packet of sperm, which is transferred to another in the process of mating. This occurs in many invertebrates. ). Oviparous (text with tooltip) An oviparous (adj.) animal is one that releases eggs in its life cycle. They may be fertilized internally or externally. .
    • Development: Development may include larval form that is markedly different from adult.
  • C. Ecology: Mainly terrestrial, a few have returned to water.
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By Jack R. Holt and Carlos A. Iudica. Last revised: 02/03/2013
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