INSECT ORDERS OF ECONOMIC IMPORTANCE

1. THYSANURA:

• Body relatively flat, tapered, and often covered with scales
• Compound eyes small or absent
• Antennae long, thread-like, and multi-segmented
• Abdomen with ten complete segments
• The eleventh abdominal segment elongated to form a median caudal filament
• Cerci present, nearly as long as the median caudal filament
• Styliform appendages located on abdominal segments 7-9
• Domestic species such as silverfish and firebrats may cause extensive damage to household goods.

2. ORTHOPTERA: Grasshoppers / Locusts / Crickets / Katydids

• Antennae filiform
• Mouthparts mandibulate, hypognathous
• Pronotum shield-like covering much of the thorax
• Front wings narrow, leathery (tegmina); hind wings fan-like
• Hind legs are usually adapted for jumping (hind femur enlarged)
• Tarsi 3- or 4-segmented
• Cerci short, unsegmented
• Immature is structurally similar to adults, developing wing pads often visible on the thorax.
• Orthoptera is generally regarded as a dominant group in most terrestrial habitats.
• These insects feed on all types of plants and often cause serious economic damage.
• Swarms of grasshoppers (locusts) regularly appear in parts of Africa, Asia, and the North.
• America and destroy crops over wide land areas.
• Mole crickets are major pests in lawns and golf courses in the southern United States.
• Several species of field crickets are reared commercially as fish bait.

Major Families

a. Acrididae (short-horned grasshoppers and locusts) :

Herbivores. Common in grasslands and prairies. This family includes many pest species such as the two-striped grasshopper (Melanoplus bivittatus), the differential grasshopper (M. differentialis), the African migratory locust (Locusta migratoria), and the desert locust (Schistocerca gregaria).

b. Tettigoniidae (long-horned grasshoppers and katydids):

Herbivores. Females have a long, blade-like ovipositor. Some species are pests of trees and shrubs.

c. Gryllidae (true crickets):

Herbivores and scavengers. Females have a cylindrical or needle-shaped ovipositor. This family includes the house cricket, Acheta domesticus.

c. Gryllotalpidae (mole crickets):

The front legs are adapted for digging. Most species feed on the roots of plants, but some are predatory.

3. ORDER: HEMIPTER

• The size of the insect varies from <1mm to >100mm.
• Insects have got piercing and sucking type of mouth parts.
• They may be winged or wingless. They usually have 4 wings.
• They may be soft or hard-bodied insects.
• They are brightly or lightly colored.
• Many species have glans for secreting odors waxes, and scales like coverings.
• There is a hemimetabolous type of development.
• The basal portion of the front wings of the true bus are generally thickened and colored but membranous overlapping tips are colored or transparent.
• Hind wings are entirely membranous and hidden under the front wings.
• Scutellum is usually exposed and triangular in shape.
• The beak is 3-4 segmented and the rostrum is 3-4 segmented.
• The beak arises from the front of the head and cuts backward to extend along the ventral side of the body.
• Insects feed on plant sap, seed fungi, fruit juice, and another r blood of insects and other animals including human beings.
• Many species are plant pests and few species transmit animal diseases but many are of no direct economic importance to human beings
• Somare predatorssf on some insects.
• Scents glands are present on the side of the thorax and they emit some peculiar odours for self-protection.
• Most of the species are terrestrial but some common groups are aquatic or semiaquatic.