Fundamentals of Entomology

INSECT LEG AND ITS MODIFICATIONS             Insects posses three pairs of legs, each in all the three thoracic segments. Insect legs are sub-divided into five basic segments known as Coxa, Trochanter, Femur, Tibia and Tarsus . v   Coxa : Functional basal segment, attached with thoracic pluerites. v   Trochanter : Small in size, being articulated to the coxa and forms immovable attachment with femur. v   Femur : The largest and strongest segment. v   Tibia : Long slender segment having one or more spurs at its distal end v   Tarsus : Distal segment attached to the tibia and is subdivided into sub-segments called Tarsomeres.             The basal tarsomere, often longer than others is named as the basitarsus . The last tarsomere is called pretarsus . And it has a pair of lateral claws (ungues) and pad like median Arolium . In few cases, the pretarsus bears a pair of lobes, or pulvilli , under the claws. The aroli

INSECT MOUTH PARTS AND ITS MODIFICATIONS Mouth parts of insects vary to a great extent among insects of different groups depending upon their feeding habits. The basic categories are a.     Madibulate mouth parts (feeding on solid food) b.     Haustellate mouth parts (feeding on liquid food) A typical insect mouthpart consists of, §   Labrum (upper lip) §   A pair of mandibles (primary jaw) §   A pair of maxillae (secondary jaw) §   Labium (lower lip) §   Hypopharynx (Tongue) Types of mouth parts 1. Biting and Chewing type:       Eg: Cockroach, Beetles, Grasshoppers, Lepidopteran larva a.     Labrum: A rectangular plate b.     Mandible: First pair of jaws, which has sharp incisors or teeth and grinding organs c.     Maxilla: Second pair of jaws comprising two lobes namely cardo and stripes which bears five segmented maxillary palpi. Stipes carries galea and lacinia d.

4. Antenna and its modifications Insect antenna: A pair of segmented appendage articulating with the head in front of or between the compound eyes. An antenna is divided into three parts, namely the basal scape , the median pedicel where lies the sensory organ called Johnston ’s organ , and the flagellum , composed of segments called flagellomeres. The size and form of antenna vary greatly and the following are the main modifications of insect antenna. Sl.No. Modifications Description Example 1. Setaceous Whip like , segments gradually taper towards tip Cockroach, Grass hopper. 2. Moniliform Bead like , segments rounded, equal in size Termites, Brown lace wings. 3. Filiform Thread like , segments uniform, elongate. Plant bugs, Short horned grass hopper. 4. Clavate Club like , segments taper towards base