Introduction:

• Entomology is a branch of zoology that deals with the study of insects.
• The term is derived from the Greek word Entomon= Insects and logos = study.
• Agricultural Entomology deals with the study of insects that affect agriculture.
• There are other branches of entomology, such as medical entomology, veterinary entomology, forest entomology and forensic entomology (study of insects inhabiting decomposing remains).

Insect:

• The world insect derived from the Latin word ‘Insectum’ which means ‘to cut into’.
• Insect body is divided into parts i.e. Head, Thorax and Abdomen.
• They have two pair of wings and three pairs of legs in thoracic region.
• Genital organs towards posterior end of the body and with decentralized nervous system
• They have open blood system, bilaterally symmetrical body and decentralized nervous system.

Characters of Class Insecta

• Body divided in to 3 segments: head, thorax and abdomen.
• Possess three pairs of legs, hence the name Hexapoda
• Presence of one or two pairs of wings and a pair of antennae.
• Respiration by means of internal air tubes known as trachea.
• Presence of metamorphosis (incomplete/complete) during development.
• Possess exoskeleton made up of hard cuticle which plays important role for survival.
• Excretion is mainly by malpighian tubules which help in maintaining ionic balance.