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EXTERNAL ANATOMY OF INSECTS

Entomology Schedule

Read: T&J Chap. 2, pp. 5, 7-23

Reference: Chapman, R.F. 1982.The Insects: Structure and Function, 3rd Ed. Harvard U.Press. Cambridge. 919pp Chapters I, VIII, XIV.

Basic arthropod body plan consists of segments with paired, jointed appendages.

Segment and appendages covered by cuticle or exoskeleton.

Rigid plates - sclerites

Flexible membrane connecting

Arrangement of sclerites:

Dorsal - tergum

Ventral - sternum

Joined laterally by membrane - pleura

Appendages arise from sternopleural region

Insects have three regions - tagma - composed of varying numbers of segments, which may be greatly modified from basic plan

Illustrated anatomy online

Head - number of segments debated

Archecerebrum preceeds mouth

post-oral segments

labral

ocular

antennal

intercalary

mandiblar

maxillary

labial

neck - cervical membrane and sclerites

Thorax - three segments

Prothorax - legs

Tergum is called pronotum

Mesothorax - legs, wings

Metathorax - legs, wings

Tergum of the wing-bearing segments may be highly modified

secondary segmentation

subdivided by sulci into several plates

Sternum usually consists of several separate sclerites

Pleural region sclerotized in adult insect - 3 basic plates

Legs are six segmented

Coxa - cone shaped, articulates with thorax

Trochanter - small segment, may be double, moves vertically

Femur - usually biggest, strongest part of leg

Tibia - long, thin, flexes back on femur

Tarsus - one to five subdivisions, may have pads - pulvilli

Pretarsus - ariolum, claws

Legs may be greatly modified for special functions and often have spines etc. or special grooves for cleaning parts like antennae

Wings - veination often used in identification (see diagram in Chapman 1982, p. 200)

Modifications include loss of one or both pairs

or sclerotization of forewings

Abdomen

Eleven segments plus the telson, bearing the anus

segments usually more distinct than those of head or thorax

in more advanced groups, fewer segments are visible

Anterior segments may show spiracles openings to tracheae

Cerci arise on segment 11

Genital openings on seg. 8 (males), 8 or 9 (females)

ovipositor present in many females

copulatory apparatus found in some males

 

Entomology Schedule